Circadian-friendly LED light source

ABSTRACT

Methods and apparatus for providing circadian-friendly LED light sources are disclosed. A light source is formed to include a first LED emission (e.g., one or more LEDs emitting a first spectrum) and a second LED emission (e.g., one or more LEDs emitting a second spectrum) wherein the first and second LED emissions are combined in a first ratio and in a second ratio such that while changing from the first ratio to the second ratio the relative circadian stimulation is varied while maintaining a color rendering index above 80.

This application is a continuation of U.S. application Ser. No.16/168,471, filed Oct. 23, 2018, which is a continuation of U.S.application Ser. No. 16/031,121, filed Jul. 10, 2018, now. U.S. Pat. No.10,137,277, issued Nov. 27, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/229,959, filed Aug. 5, 2016, now U.S. Pat. No.10,076,633, issued Sep. 18, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/316,685, now U.S. Pat. No. 9,410,664, issuedAug. 9, 2016. Filed Jun. 26, 2014, now U.S. Pat. No. 9,410,664, issuedAug. 9, 2016, which claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 61/871,525 filed on Aug. 29, 2013, which isincorporated by reference in its entirety.

FIELD

The disclosure relates to the field of illumination products and moreparticularly to apparatus and methods for providing circadian-friendlyLED light sources.

BACKGROUND

Identification of non-visual photoreceptors in the human eye (so-calledintrinsically photosensitive retinal ganglion cells, or “ipRGCs”) linkedto the circadian system has sparked considerable interest in the effectsof various light spectra on health and amenity for human beings. Highcircadian stimulation may lead to positive effects such as resettingsleep patterns, boosting mood, increasing alertness and cognitiveperformance, and alleviating seasonal affective depression. However,mis-timed circadian stimulation can also associated with disruption ofthe internal biological clock and melatonin suppression, and may belinked to illnesses such as cancer, heart disease, obesity and diabetes.

Circadian stimulation is associated with glucocorticoid elevation andmelatonin suppression and is most sensitive to light in the bluewavelength regime. With the preponderance of light-emitting diode (LED)illumination products being based on blue-primary phosphor-convertedwhite-emitting LEDs, the situation has developed that most LED-basedillumination sources have higher levels of circadian stimulation thanthe traditional sources they are intended to replace.

In addition, illumination products are rarely tunable (other than meredimming), and legacy illumination products fail to address the impact onhumans with respect to diurnal or circadian cycles. Still worse, legacyillumination products that are ostensibly tunable fail to produce goodcolor rendering throughout the tunable range.

What is needed is a technique or techniques for constructingillumination products in which light emission (e.g., LED light emission)can be controlled to provide varying levels of circadian stimulationwhile providing desirable light quality aspects such as correlated colortemperature (CCT) and color rendering index (CRI). Also needed is anillumination system in which a first ratio and a second ratio of lightemission are such that changing from the first ratio to the second ratiovaries relative circadian stimulation while maintaining a CRI above 80and maintaining the CCT within a prescribed range.

The aforementioned legacy technologies do not have the capabilities toimplement a circadian-friendly LED light source in an efficient manner.Therefore, there is a need for improved approaches.

SUMMARY

Regarding human circadian system stimulation, positive benefits can berealized and the deleterious ones avoided by stimulating a circadianlight cycle in a way similar to that which occurs in nature (sunlightaction over the course of the day), i.e., bright illumination levelsassociated with high blue content in the morning and midday, and lowerlight levels and greatly reduced blue content in the evenings.

The embodiments disclosed herein describe how to make and use variouscombinations of different LED emission spectra, and how to make whitelight sources that can be tuned to cycle through ranges fromhigh-circadian-stimulating light to less-circadian-stimulating lightwhile maintaining reasonable color rendering (CRI>80 and R9>0) and whitecolor point.

In a first aspect, light sources are provided comprising at least onefirst LED emission source characterized by a first emission; and atleast one second LED emission source characterized by a second emission;wherein the first emission and the second emission are configured toprovide a first combined emission and a second combined emission, thefirst combined emission is characterized by a first SPD and fractionsFv1 and Fc1; the second combined emission is characterized by a secondSPD and fractions Fv2 and Fc2; Fv1 represents the fraction of power ofthe first SPD in the wavelength range from 400 nm to 440 nm; Fc1represents the fraction of power of the first SPD in the wavelengthrange from 440 nm to 500 nm; Fv2 represents the fraction of power of thesecond SPD in the wavelength range from 400 nm to 440 nm; Fc2 representsthe fraction of power of the second SPD in the wavelength range from 440nm to 500 nm; the first SPD and the second SPD have a color renderingindex above 80; Fv1 is at least 0.05; Fc2 is at least 0.1; and Fc1 isless than Fc2 by at least 0.02.

In a second aspect, display systems are provided comprising a first LEDemission source characterized by a first emission; and a displayconfigured to emit a first SPD characterized by a first fraction Fv1 ofpower in the range 400 nm to 435 nm; wherein, the display system ischaracterized by a color gamut of at least 70% of NTSC; the first SPD issubstantially white with a CCT in a range from 3000K to 9000K; and Fv1is at least 0.05.

In a third aspect, light sources are provided comprising an LED deviceconfigured to emit a primary emission; one or more wavelength conversionmaterials optically coupled to the primary emission; wherein a portionof the primary emission is absorbed by the wavelength conversionmaterials to produce a secondary emission; wherein a combination of theprimary emission and the secondary emission produces white lightcharacterized by an SPD having a CCT and a color rendering index;wherein at least 5% of the SPD power is in a wavelength range from 400nm to 435 nm; wherein a circadian stimulation of the SPD is less than80% of a circadian stimulation of a reference illuminant having the samecolor temperature; and wherein the white light is characterized by acolor rendering index above 80.

In a fourth aspect, lighting systems are provided comprising an LEDdevice configured to emit a primary emission characterized by a primarySPD; at least one phosphor optically coupled to the primary emission,wherein the at least one phosphor is characterized by saturableabsorption within a blue-cyan wavelength region; wherein the LED deviceis configured to be controlled by a power signal configured to dim theprimary emission; wherein at a first power level the system emits afirst SPD characterized by a first fraction fc1 of spectral power in awavelength range from 440 nm to 500 nm and a first CCT; wherein at asecond power level the system emits a second SPD characterized by asecond fraction fc2 of spectral power in a wavelength range from 440 nmto 500 nm and a second CCT; and wherein the second power level is lessthan the first power level and the second fraction fc2 is less than 80%of the first fraction fc1.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art will understand that the drawings, describedherein, are for illustration purposes only. The drawings are notintended to limit the scope of the present disclosure.

FIG. 1A is a diagram showing a circadian stimulation wavelength range asused to tune a circadian-friendly LED light source, according to someembodiments.

FIG. 1B shows how the impact of a light source on the circadian systemscales against relative measures.

FIG. 1C shows a relative circadian stimulation for 3300K white lightsources composed of a primary LED (violet- to blue-emitting) combinedwith a green-emitting and red-emitting phosphor for different full-widthhalf-maxima of circadian stimulation wavelength ranges peaked at 465 nm,according to some embodiments.

FIG. 1D shows SPDs for 3300K white light sources composed of a primaryLED (violet- to blue-emitting) combined with a green-emitting andred-emitting phosphor, normalized to emission at 600 nm according tosome embodiments.

FIG. 1E shows the circadian stimulation for a two-phosphor based LEDwhite light source at 3300K as a function of the primary LED emissionpeak wavelength, according to some embodiments.

FIG. 1F shows predicted melatonin suppression versus illuminance at theeye level, for a 90 min exposure, according to some embodiments.

FIG. 2A shows LED spectral power distributions (SPDs) of wavelengthcombinations as used in configuring a circadian-friendly LED lightsource, according to some embodiments.

FIG. 2B shows an SPD corresponding to a first LED emission as used inconfiguring a circadian-friendly LED light source, according to someembodiments.

FIG. 2C shows an SPD corresponding to a second LED emission as used inconfiguring a circadian-friendly LED light source, according to someembodiments.

FIG. 3A is a chart showing color rendering properties exhibited by acircadian-friendly LED light source at three different colortemperatures, according to some embodiments.

FIG. 3B is a chart showing relative circadian stimulation resulting froma circadian-friendly LED light source at three different colortemperatures, according to some embodiments.

FIG. 4A shows an example of a light strip used to implement an LED whitelight source that is tunable based on measurable aspects and/or changesin the environment, according to some embodiments.

FIG. 4B shows a narrower band (Gaussian) circadian stimulation rangewith 30 nm full-width-half-maximum (FWHM) and peaked at 465 nm.

FIG. 4C1 and FIG. 4C2 show emission of a first violet-pumpedtwo-phosphor LED and a second violet-pumped blue-phosphor LED,respectively, according to some embodiments.

FIG. 4D1 shows the individual and combined LED-based emission spectra ofFIG. 4C1 and FIG. 4C2.

FIG. 4D2 shows differences in color properties and levels of circadianstimulation, according to some embodiments.

FIG. 4E1 and FIG. 4E2 show emission of a first violet-pumpedtwo-phosphor LED and a second blue-emitting LED, respectively, accordingto some embodiments.

FIG. 4F1 shows the individual and combined LED-based emission spectra ofFIG. 4D1 and FIG. 4D2.

FIG. 4F2 shows differences in color properties and levels of circadianstimulation, according to some embodiments.

FIG. 4G shows circadian stimulation as a function of color temperaturefor certain light sources.

FIG. 4H shows a light strip having two different sets of LEDs andcontrolled by a clock to adjust the ratio of LED emission wavelength toimplement a circadian-friendly LED light source, according to someembodiments.

FIG. 4I shows SPDs for two display systems with a white screen,according to some embodiments.

FIG. 4J shows predicted melatonin suppression, according to someembodiments.

FIG. 4K shows the spectrum emitted by a white screen, according to someembodiments.

FIG. 4L1 and FIG. 4L2 illustrate the situation for a typical LED-litliquid crystal display, according to some embodiments.

FIG. 4M shows calculated relative circadian stimulation and relativedisplay efficacy.

FIG. 4N1 and FIG. 4N2 show situations for which the phosphor system istuned to better work with a chosen primary peak emission wavelength,according to some embodiments.

FIG. 5A is a chart showing a linear chromaticity curve in x-ychromaticity space as produced by a circadian-friendly LED light source,according to some embodiments.

FIG. 5B is a chart showing the shape of a white light bounding region asproduced by a circadian-friendly LED light source, according to someembodiments.

FIG. 5C1 through FIG. 5C4 show characteristics of two sets of LEDs thatare controlled independently, according to some embodiments.

FIG. 6A shows an exploded view and FIG. 6B shows an assembly view of aLED lamp employing a circadian-friendly LED light source, according tosome embodiments.

FIG. 7 shows a schematic of a multi-track driver control system as usedin an LED lamp employing a circadian-friendly LED light source,according to some embodiments.

FIG. 8 shows two strings of LEDs in an intermixed physical arrangementto form a two-track, circadian-friendly arrangement as used in an LEDlamp, according to some embodiments.

FIG. 9A presents a selection of lamp shapes corresponding to variousstandards, according to some embodiments.

FIG. 9B through FIG. 9I present selections of troffers corresponding tovarious shapes, according to some embodiments.

FIG. 10A through FIG. 10I depict embodiments of the present disclosurein the form of lamp applications according to some embodiments.

FIG. 11A shows an initial SPD of a LED white light source, and afiltered SPD after blue light is removed, according to some embodiments.

FIG. 11B shows an initial SPD of a LED white light source and aconverted SPD after blue light is absorbed by a phosphor and convertedto yellow light, according to some embodiments.

FIG. 12 shows an emission spectrum of a LED white light source with aCCT of 3000K and a CRI of about 90, and the emission and absorptionspectra of a saturable red phosphor, according to some embodiments.

FIG. 13 shows a possible way to combine a LED white light source withsuch a saturable phosphor, according to some embodiments.

FIG. 14A and FIG. 14B show spectral and colorimetric properties,respectively, of a LED lighting system, according to some embodiments.

FIG. 15A1 Through FIG. 15I depict lighting applications.

DETAILED DESCRIPTION

Reference is now made in detail to certain embodiments. The disclosedembodiments are not intended to be limiting of the claims.

Non-visual photoreceptors in the human eye (so-called intrinsicallyphotosensitive retinal ganglion cells) are linked to the circadiansystem. While details of the circadian excitation band continue toevolve, a common consensus is that it the excitation band is peaked inthe blue range at around 465 nm.

FIG. 1A is a diagram 1A00 showing a circadian stimulation wavelengthrange (CSWR) 102 as used to tune a circadian-friendly LED light sourceas presented by Brainard et al. in The Journal of Neuroscience, Aug. 15,2001, 21(16):6405-6412 (Brainard), compared to the photopic vision range104. With such a broad effective action spectrum, it appears there islittle one can do to vary circadian stimulation for a white lightsource, other than varying the relative short-wavelength content, thatis, the CCT. However, more recent work suggests that the relevant CSWRis in fact much narrower than presented in Brainard et al. For example,in Rahman et al., Endocrinology, Aug. 7, 2008, 149(12):6125-6135, it isshown that glucocorticoid elevation and melatonin suppression may beavoided by filtering blue light in a wavelength range of only 450 nm to480 nm. This is significant because a narrower CSWR means there shouldbe more flexibility in designing a white light source for desirablequality of light, while also controlling the amount of circadianstimulation. Further, it is noteworthy that Brainard et al. imposed asymmetric shape for their action spectrum when fitting experimentaldata; however, a careful analysis of the experimental points in FIG. 5of Brainard et al. shows that the experimental response at shortwavelength (e.g., 420 nm) is significantly lower than is obtained by thefitted curve. In other words, there is suggestive evidence that the CSWRis not well-known, especially at short wavelength, and may be narrowerthan is reported in some action spectra.

Circadian stimulation (CS) via ipRGCs for an illuminant with a spectralpower distribution SPD as a function of wavelength, k, can be modeledas:

${CS} = \frac{\int{c(\lambda){{SPD}(\lambda)}d\lambda}}{\int{{{SPD}(\lambda)}d\lambda}}$where c(λ) is the circadian stimulation spectrum. For two illuminants Aand B of equal luminous flux (relevant for illumination applications),the relative Circadian Stimulation (CS) of A vs. B is:

$\frac{CS_{A}}{CS_{B}}.\frac{LE_{B}}{LE_{A}}$where LE is the lumen equivalent of the spectral power distribution.

FIG. 1B shows how the impact of a light source on the circadian systemscales against light intensity. The impact of a light source on thecircadian system scales with relative CS, with light intensity (e.g.,lux level), and with exposure time. One can combine the relative CS andthe data from monochromatic stimuli disclosed by Brainard. One thenobtains FIG. 1B which shows the melatonin suppression for variousilluminances and for various light sources.

FIG. 1B shows melatonin suppression as a function of illuminance (lux)reaching the human eye, after a 90 min exposure. Curve 111 shows theresponse to monochromatic radiation at 460 nm, and is directly takenfrom Brainard. Curve 112 shows the response to standard illuminant D65.Curve 113 shows the response to illumination by standard illuminant A.Curves 112 and 113 are obtained by shifting curve 111, according totheir relative CS.

FIG. 1B shows that for a common indoor residential lighting situation(300 lx under illuminant CIE A, representative of an incandescent lamp)melatonin suppression is significant: about 50% after 90 min. Thus, evenin this common situation the circadian system can be impacted. For lightsources with a larger relative CS than illuminant A, the effect can bestronger.

The following figures and text serve to compare the relative CS betweenvarious LED white light sources. FIG. 1C shows a relative circadianstimulation (CS) for 3300K white light sources composed of a primary LED(varying from violet- to blue-emitting) combined with a green-emittingand a red-emitting phosphor. In FIG. 1C, the x-axis is the centeremission wavelength of the primary LED and the y-axis is the relativecircadian stimulation (normalized to CIE A). The circadian stimulationis calculated assuming a circadian stimulation wavelength range peakedat 465 nm, with a Gaussian line shape and with various full-widthhalf-maxima (from 10 nm to 90 nm) as labeled on the figure (see FIG.1A). Regarding the phosphors used to obtain the white light source,suitable phosphors may be Eu²⁺ doped materials. An example of agreen-emitter is BaSrSiO:Eu²⁺. An example of a red-emitter isCaAlSiN:Eu²⁺. In FIG. 1C, the green and red emission peakwavelength/FWHM are 530/100 and 630/100, respectively. Other phosphorsare also possible, as described below. In addition to phosphors, otherwavelength down-converting materials may be used, such as organicmaterials or semiconductors such as nanoparticles otherwise known as“quantum dots”. In other embodiments, the green and/or red emission maybe provided by LEDs. As shown in FIG. 1C, for wide CSWRs (e.g., wide 90nm 123 and wide 70 nm 124) there is little primary LED wavelengthsensitivity, or even a penalty as the wavelength gets too short.However, for narrower CWSRs (e.g., 10 nm 121 and 30 nm 122), there is astrong benefit to reducing the primary LED wavelength. For example, fora 30 nm FWHM CSWR 122, the relative CS for a violet (˜405 nm to 425 nm)primary 3300K LED is about half that of the CIE A illuminant (2856K)125. Thus, light source 122 is less circadian stimulating than manyincandescent lamps, and dramatically less stimulating than a 445 nm(blue) based 3300K LED 123, which has a CS about 20% higher than CIE A.SPDs for various LED light source emissions including those of FIG. 1Care shown in FIG. 1D, normalized to emission at 600 nm. The SPDs arecharacterized, for example, by different violet content. For each SPD,CRI is maintained at 80 or higher and R9 is above zero (about 10).

Non- or weakly-circadian-stimulating light sources are desirable, forexample, for evening illumination, in order to avoid glucocorticoidelevation and melatonin suppression, and thus prepare people for healthysleep. Referring to the 30 nm FWHM CSWR of FIG. 1C, FIG. 1E shows the CSfor a two-phosphor based LED white light source at 3300K as a functionof the primary LED emission peak wavelength. For a 455 nm primaryemission, the lumen equivalent of the SPD is high (about 320 lm/Wopt),but the CS is also high (about twice that of CIE A). As the primary LEDpeak wavelength is reduced below 455 nm, the CS falls dramatically.Further, as the primary LED peak wavelength is reduced below 420 nm, theLE also decreases. Thus, there is a range of primary LED peak emissionwavelengths where the LE is still reasonably high, but the CS is reducedrelative to CIE A. In particular, the wavelength range of 405 nm to 435nm provides reduced CS and reasonable LE. A variety of standard LEDsources with this CCT have a LE of about 300, therefore embodiments withan LE of about 200 or about 250 can be considered acceptable as theyprovide a much lower CS than standard sources.

FIG. 1F further illustrates the advantage of such light sources. FIG. 1Fshows predicted melatonin suppression versus illuminance at the eyelevel, for a 90 min exposure. Curve 1 corresponds to an LED source with415 nm primary peak emission, and curve 2 corresponds to an LED sourcewith 455 nm primary peak emission. Due to the lower relative CS, the 415nm-primary LED induces less melatonin suppression. If the light level isdimmed to about 100 lux, the suppression becomes very small (less than10% above the ceiling of the signal) whereas for the same illuminanceunder the 455 nm-primary LED, melatonin suppression is significant(about 40% in 90 min). Thus, the change in circadian stimulation has arelevant impact in a realistic environment.

In principle, another approach can be used to reduce the circadianstimulation of a light source: tuning the CCT of the lightsource—indeed, a warmer CCT generally leads to a lower relative CS.Various LED-based products provide this capability. However theseproducts employ blue primary LEDs (peak emission wavelength range fromabout 445 nm to 460 nm). Therefore, even at low CCT, the relative CSremains fairly high (e.g., about twice that of illuminant CIE A for a3000K LED source, as shown, for example, in FIG. 1C).

Therefore, careful choice of the emission wavelength of the primary LEDand of the overall emission spectrum of the primary LED is important tosignificantly modulate CS.

Embodiments of various circadian-friendly LED white light sources can beconfigured such that the respective emission spectra can be tuned so asto simulate a circadian cycle in a more or less daily diurnal cycle.

FIG. 2A shows spectral power distributions (SPDs) of various wavelengthcombinations 2A00 as used in configuring a circadian-friendly LED whitelight source.

As shown in FIG. 2A, a stimulating blue peak is emitted for morningcircadian stimulation (see curve 202). Another curve exhibits lowcircadian stimulation (see curve 206) for evenings, and a third curve(204) shows an intermediate option.

In certain embodiments, a circadian-friendly LED white light source(e.g., see luminaire of FIG. 4A and lamp of 6A and FIG. 6B) includes afirst LED (see FIG. 2B) such as a violet (or UV) primary LED combinedwith a green, red, and (optional) blue phosphor to emit a spectrum 208that is substantially a low-circadian-stimulating spectrum at acorrelated color temperature (CCT) of 2500K (see spectrum of LEDemissions 208 in FIG. 2B). Such an LED and phosphor combination canexhibit a reasonable white color point and can exhibit reasonable colorrendering properties. Depending on the details such as the emissionspectra of the primary LED and phosphors, it may not be necessary tocombine a blue phosphor with a first LED.

For implementation of a circadian-friendly LED light source, a secondLED (see FIG. 2C) can be added. The emission 210 (FIG. 2C) can begenerated by using a second LED comprising, for example, a violet (orUV) LED to pump only a blue phosphor. The blue phosphor can be selectedbased on absorption characteristics of photons from the primary (violetor UV) LED: namely, is the blue phosphor can be chosen such thatexcitation can occur for moderate phosphor loading, such that theresulting system package efficiency is sufficient. Also, a blue phosphorcan be selected based on the emission properties of the combination soas to combine with the first LED emission, thus shifting or tuning thechromaticity in a controlled manner (e.g., in a direction similar toincreasing CCTs along the Planckian curve to maintain a white lightappearance). In addition, a blue phosphor peak emission wavelength andFWHM can be selected to maintain specified color rendering propertieseven as the contribution of the second LED to the total spectrum (firstand second LED combined) is increased (FIG. 2A). In some cases, thedesired color rendering properties can be expressed as a CRI above 50, aCRI above 80, or in certain embodiments, a CRI above 90. Other metricssuch as R9, another color fidelity metric, and/or a color gamut metriccan also be employed. In some embodiments, a blue phosphor may be a mixof different phosphors, which, combined together, give the desiredexcitation and emission properties including the desired dominantwavelength of emission for spectral tuning as described herein.

For an SPD with a CCT of 2500K, the fraction of power in the spectralrange from 400 nm to 440 nm is 0.03 and the fraction of power in therange from 440 nm to 500 nm is 0.06. For an SPD with a CCT of 5000K, thefraction of power in the spectral range from 400 nm to 440 nm is 0.02and the fraction of power in the range from 440 nm to 500 nm is 0.20.

Certain color rendering properties for LED white light sources providedby the present disclosure at various LED temperatures are illustrated inFIG. 3A. The circadian stimulation (relative to a CIE A illuminant),based on a CSWR modeled after Brainard (102 in FIG. 1A, about 95 nmFWHM) is illustrated in FIG. 3B.

Certain embodiments use a blue phosphor characterized by a 477 nm peakemission wavelength and a FWHM of 80 nm. Such blue phosphors with a 477nm peak emission wavelength represents only one embodiment and otherembodiments use other phosphors and phosphor combinations. Inparticular, the phosphors and/or compositions of wavelength-conversionmaterials referred to in the present disclosure may comprise variouswavelength-conversion materials.

Wavelength conversion materials can be ceramic or semiconductor particlephosphors, ceramic or semiconductor plate phosphors, organic orinorganic downconverters, upconverters (anti-stokes), nano-particles,combinations of any of the foregoing and other materials which providewavelength conversion. Some examples are listed below:

-   -   (Srn,Ca_(1−n))10(PO₄)₆.B₂O₃:Eu²⁺ (where 0≤n≤1)    -   (Ba,Sr,Ca)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺,Mn²⁺    -   (Ba,Sr,Ca)BPO₅:Eu²⁺,Mn²⁺    -   Sr₂Si₃O₈.₂SrCl₂:Eu²⁺    -   (Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺,Mn²⁺    -   BaAl₈O₁₃:Eu²⁺    -   2SrO._(0.84)P₂O₅._(0.16)B₂O₃:Eu²⁺    -   (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²⁺,Mn²⁺    -   K₂SiF₆:Mn⁴⁺    -   (Ba,Sr,Ca)Al₂O₄:Eu²⁺    -   (Y,Gd,Lu,Sc,La)BO₃:Ce³⁺,Tb³⁺    -   (Ba,Sr,Ca)₂(Mg,Zn)Si₂O₇:Eu²⁺    -   (Mg,Ca,Sr,Ba,Zn)₂Si_(1−x)O_(4−2x):Eu²⁺ (where 0≤x≤0.2)    -   (Ca,Sr,Ba)MgSi₂O₆: Eu²⁺    -   (Sr,Ca,Ba)(Al,Ga)₂S₄:Eu²⁺    -   (Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu²⁺,Mn²⁺    -   Na₂Gd₂B₂O₇:Ce³⁺,Tb³⁺    -   (Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu²⁺ Mn²⁺    -   (Gd,Y,Lu,La)₂O₃:Eu³⁺,Bi³⁺    -   (Gd,Y,Lu,La)₂O₂S:Eu³⁺,Bi³⁺    -   (Gd,Y,Lu,La)VO₄:Eu³⁺,Bi³⁺    -   (Ca,Sr)S:Eu²⁺,Ce³⁺    -   (Y,Gd,Tb,La,Sm,Pr,Lu)₃(Sc,Al,Ga)_(5−n)O_(12−3/2n):Ce³⁺ (where        0≤n≤0.5)    -   ZnS:Cu⁺,Cl⁻    -   (Y,Lu,Th)₃Al₅O₁₂:Ce³⁺    -   ZnS:Cu⁺,Al³⁺    -   ZnS:Ag⁺,Al³⁺    -   ZnS:Ag⁺,Cl⁻    -   The group:    -   Ca_(1−x)Al_(x−xy)Si_(1−x+xy)N_(2−x−xy)C_(xy):A    -   Ca_(1−x−z)Na_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy)C_(xy):A    -   M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy)C_(xy):A    -   M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy−2w/3)C_(xy)O_(w−v/2)H_(v):A    -   M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy−2w/3−v/3)C_(xy)O_(w)H_(v):A    -   wherein 0<x<1, 0<y<1, 0≤z<1, 0≤v<1, 0<w<1, x+z<1, x>xy+z, and        0<x−xy−z<1, M(II) is at least one divalent cation, M(I) is at        least one monovalent cation, M(III) is at least one trivalent        cation, H is at least one monovalent anion, and A is a        luminescence activator doped in the crystal structure.    -   LaAl(Si_(6−z)Al_(z))(N_(10−z)O_(z)):Ce³⁺ (where z=1)    -   (Ca,Sr)Ga₂S₄:Eu²⁺    -   AlN:Eu²⁺    -   SrY₂S₄:Eu²⁺    -   CaLa₂S₄:Ce³⁺    -   (Ba,Sr,Ca)MgP₂O₇:Eu²⁺,Mn²⁺    -   (Y,Lu)₂WO₆:Eu³⁺,Mo⁶⁺    -   CaWO₄    -   (Y,Gd,La)₂O₂S:Eu³⁺    -   (Y,Gd,La)₂O₃:Eu³⁺    -   (Ba,Sr,Ca)_(n)Si_(n)Nn:Eu²⁺ (where 2n+4=3n)    -   Ca₃(SiO₄)O₂:Eu²⁺    -   (Y,Lu,Gd)_(2−n)Ca_(n)Si₄N_(6+n)C_(1−n):Ce³⁺ (where 0≤n≤0.5)    -   (Lu,Ca,Li,Mg,Y) alpha-SiAlON doped with Eu²⁺ and/or Ce³⁺    -   (Ca,Sr,Ba)SiO₂N₂:Eu²⁺,Ce³⁺    -   Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺    -   (Sr,Ca)AlSiN₃:Eu²⁺    -   CaAlSi(ON)₃:Eu²⁺    -   Ba₃MgSi₂O₈:Eu²⁺    -   LaSi₃N₅:Ce³⁺    -   Sr₁₀(PO₄)₆Cl₂:Eu²⁺    -   (BaSi)O₁₂N₂:Eu²⁺    -   M(II)_(a)Si_(b)O_(c)N_(d)C_(e):A where 6<a<8, 8<b<14, 13<c<17,        5<d<9, 0<e<2 and M(II) is a divalent cation of        (Be,Mg,Ca,Sr,Ba,Cu,Co,Ni,Pd,Tm,Cd) and A of        (Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Mn,Bi,Sb)    -   SrSi₂(O,Cl)₂N₂:Eu²⁺    -   SrSi₉Al₁₉ON₃₁:Eu²⁺    -   (Ba,Sr)Si₂(O,Cl)₂N₂:Eu²⁺    -   LiM₂O₈:Eu³⁺ where M=W or Mo

For purposes of the application, it is understood that when a phosphorhas two or more dopant ions (e.g., those ions following the colon in theabove phosphors), this is to mean that the phosphor has at least one(but not necessarily all) of those dopant ions within the material. Thatis, as understood by those skilled in the art, this type of notationmeans that the phosphor can include any or all of those specified ionsas dopants in the formulation.

Further, it is to be understood that nanoparticles, quantum dots,semiconductor particles, and other types of materials can be used aswavelength converting materials. The list above is representative andshould not be taken to include all the materials that may be utilizedwithin the embodiments described herein.

Embodiments of lamps can include any of the aforementioned wavelengthconversion materials, and can exhibit various qualities of lightcharacteristics. Some of such qualities of light characteristics areshown in FIG. 3A and FIG. 3B.

FIG. 3A is a color rendering chart 3A00 showing color rendering index(Ra) and red color rendering (R9) exhibited by a circadian-friendly LEDwhite light source of FIG. 2A at three different color temperatures(e.g., 5000° K, 3500° K, and 2500° K).

When the first and second LED emissions are combined in comparablelevels, a 5000K color point can be achieved with acceptable colorrendering (Ra, R9 of 80, 65 respectively). Moreover, this emissionspectrum can have a high relative circadian stimulation (as definedabove) similar to that achieved with a D65 reference illuminant(daylight). When the second LED emission is reduced to a very low level(or turned off), the first LED emission dominates, and alow-circadian-stimulating spectrum is achieved at 2500K with Ra, R9 of93, 65. At an intermediate point, a 3500K color temperature is providedwith Ra, R9 of 85, 88 and a mid-level stimulation of the circadiansystem. Accordingly, this LED white light source can be used to achievehigh-stimulating 5000K light in the morning, 3500K mid-stimulatingillumination in the afternoon, and low-stimulating 2500K light in theevening, all while maintaining acceptable white light quality (Ra≥80,R9≥50). Total power to the first and second LEDs may be adjusted toprovide the desired total illuminance levels.

FIG. 3B is a chart 3B00 showing relative circadian stimulation resultingfrom a circadian-friendly LED light source.

FIG. 3B shows the relative circadian stimulation of thecircadian-friendly light source illustrated in FIG. 2A, using a 95 nmFWHM CSWR as modeled after Brainard. By combining both first and secondLED emissions to achieve a color temperature of 5000K (202 in FIG. 2A),a very high circadian stimulating effect is achieved. As shown in FIG.3B, at 5000K the relative circadian stimulation is approximately 2.8times higher than that of the CIE A reference illuminant. This level ofcircadian stimulation is close to that achieved with an illuminantassociated with daylight (e.g., D65 illuminant, as shown), which has arelative circadian stimulation 3.1 times higher than that of the CIE Areference illuminant. When the second LED is turned down (or off) sothat the first LED emission dominates, the 2500K spectrum is achieved(206 in FIG. 2A), which has a very low circadian stimulation (within 10%of that of the CIE A reference illuminant). When the intensity of thefirst and second LED emission are comparable, an intermediate spectrumat 3500K is achieved (204 in FIG. 2A), which provides a relativecircadian stimulation about two times higher than that of the CIE Areference illuminant.

The color may be changed dynamically (either continuously or stepwise)throughout the day, via a clock-controlled driving scheme. Or, thedesired color point may be selected using a switching mechanism providedfor the end user. Many other automatic and/or human-interface controlschemes may be employed, such as power-line communication, WiFi, Zigby,DALI, etc. Different target CCTs are also possible. It is expected thatsuch a light source would have dramatic benefits for health and amenitycompared to circadian-unfriendly light sources such as standardblue-based LEDs.

FIG. 4A shows an example of a light strip used to implement a whitelight source that is tunable based on measurable aspects (e.g., time ofday) and/or changes in the environment. Such a white light source can beformed, for instance, by mixing at least two LED-based sources: e.g., afirst using an appropriate mix one set of red-, green- and (optional)blue-emitting phosphors with violet-primary LEDs, and a second usingeither violet-pumped blue phosphor LEDs or blue-primary LEDs. The twosources can be mixed throughout a diurnal cycle to form acircadian-friendly LED white light source. Such a light strip may beused, for example, as a light engine for a linear troffer luminaire.

In other embodiments, the CSWR can be narrower than described byBrainard (curve 401 in FIG. 4B). For example, consider a 465 nm peakGaussian CSWR with a FWHM of 30 nm as shown as curve 402 in FIG. 4B. Forthis narrower CSWR, it is possible to design LED white light sourceshaving a CCT higher than that of CIE A, but with lower circadianstimulation.

FIG. 4C1 shows a first LED emission 4C100 of a violet-primary LEDpumping a green and red phosphor 403. This emission is at 3286K but hasa CS 50% relative to CIE A. Thus, the LED white light source has ahigher CCT than CIE A but a lower circadian stimulation. The second LEDemission 4C200 (FIG. 4C2) is a violet primary LED pumping a bluephosphor having a peak emission wavelength of 477 nm 404. The first andsecond LED-based emissions can be combined, as shown in FIG. 4D1, totune from about 5000K to about 3300K, varying the CS from about 300% toless than 50% that of CIE A, while maintaining a white point within 4points of the Planckian, a CRI>80, and an R9>10, as shown in the tablein FIG. 4D2.

This change in CS can also be quantified by considering the relativespectral content (e.g., fraction of the SPD) in specific spectralranges. Two ranges of interest are the relative spectral content in the‘violet-blue’ (VB) range 400 nm to 440 nm and in the ‘blue-cyan’ (BC)range 440 nm to 500 nm. The former range is relatively lesscircadian-stimulating, and the latter range is relatively morecircadian-stimulating. The table in FIG. 4D2 shows the relative spectralcontent for these wavelength ranges. When tuning from 5000K to 3300K,the fraction of total SPD power in the VB range increases slightly (from0.19 to 0.23) whereas the fraction in the BC range decreasessignificantly (from 0.20 to 0.05). This re-apportioning of the spectralcontent from the BC range to the VB range contributes to the low CS ofthe 3300K SPD. Also, note that the presence of violet light enables theSPD to remain on-Planckian.

In certain embodiments, having a large fraction Fv of the SPD in the VBrange or a small fraction Fc in the BC range corresponds to a low CS,and vice-versa. For example, an SPD characterized by a Fc>0.1 may have ahigh stimulation, and an SPD characterized by a Fc<0.06 and Fv>0.05 mayhave a low stimulation. Similarly, an SPD characterized by a Fc/Fv>0.5may have relatively high stimulation, and an SPD characterized by aFc/Fv>1 may have a high stimulation. An SPD characterized by a Fc/Fv<0.4may have a relatively low stimulation and an SPD characterized by aFc/Fv<0.2 may have a low stimulation. These ranges correspond to certainembodiments of LED white light sources provided by the presentdisclosure, including those of FIGS. 4A-4N2 and FIGS. 5A-5C4.

Therefore, the CS can, in general, be proportional to the ratio Fc/Fv,with higher values being associated with greater circadian stimulation.CS can also, in general, be proportional to the Fc content. Furthermore,in certain embodiments, increasing the VB content of a LED white lightsource will decrease the BC content, and conversely increasing the BSwill result in reduced VB content.

Fv and Fc represent the fraction of power in the SPD within either theVB wavelength range or the BC wavelength range, respectively. Forexample, where the total power in the SPD is 1, when 10% of the power inthe SPD is in the VB wavelength range, Fv is 0.1; and when 10% of thepower of the SPD is in the BC wavelength range, Fc is 0.1.

In certain embodiments, Fv is less than 0.2, less than 0.15, less than0.1, less than 0.08, and in certain embodiments, less than 0.05.

In certain embodiments, Fv is greater than 0.2, greater than 0.15,greater than 0.1, greater than 0.08, and in certain embodiments, greaterthan 0.05.

In certain embodiments, Fc is less than 0.2, less than 0.15, less than0.1, less than 0.08 and in certain embodiments, less than 0.05.

In certain embodiments, Fc is greater than 0.2, greater than 0.15,greater than 0.1, greater than 0.08, and in certain embodiments, greaterthan 0.05.

Various combinations of Fv and Fc can be provided consistent withproviding a LED white light source of the present disclosure. It issignificant that using the devices and methods provided by the presentdisclosure, Fv, i.e., the spectral content in the VB range from 400 nmto 440 nm can be controlled to provide a desired white light emissionand maintain desired attributes such as CCT, CRI, Ra, Duv, and others.Use of violet emitting LEDs and select phosphors, and optionallyadditional LEDs emitting at other wavelengths, provide the ability tomore accurately control the content in the VB range from 400 nm to 440nm.

In certain embodiments, Fc/Fv is from 0.1 to 1, from 0.1 to 0.8, from0.1 to 0.6, and in certain embodiments, from 0.1 to 0.4.

In certain embodiments, Fc/Fv is less than 0.1, less than 0.2, less than0.3, less than 0.4, less than 0.5, and in certain embodiments, less than0.6.

In certain embodiments, Fc/Fv is from 0.5 to 1.5, from 0.5 to 1.3, from0.5 to 1.1, and in certain embodiments, from 0.5 to 0.9.

In certain embodiments, Fc/Fv is greater than 0.5, greater than 0.6,greater than 0.7, greater than 0.8, greater than 0.9, and in certainembodiments, greater than 1.

It should be appreciated that it is not trivial to obtain the highquality of light demonstrated by the embodiments of the presentdisclosure. Although one can reduce the CS of a light source by simplyremoving all (or most) of the blue and cyan emission—withoutsupplementing it with violet radiation, the resultant color renderingindex would be poor because of the absence of short-wavelength light inthe spectrum. Furthermore, it can be difficult to maintain thechromaticity of a source near-Planckian (resulting in a source with alow CCT and/or a greenish tint). In contrast, embodiments of the presentdisclosure balance the amount of blue and violet light and therebyfacilitate modulating the CS while maintaining high quality of light(e.g., CRI, Ra, Duv).

It is possible for a second LED emission to use a primary blue-emittingLED with a suitable dominant wavelength to tune along the Planckian. Forexample, as shown in FIG. 4E1 and FIG. 4E2, an about 480 nm peakemission LED may be used in place of the blue-phosphor-based LED of FIG.4C2. FIG. 4E1 shows an emission spectrum of a first LED-based source 420and FIG. 4E2 shows a spectrum 421 of a blue-emitting LED. By combiningthe emissions shown in FIG. 4E1 and FIG. 4E2, a similar effect isachieved as shown by the combined spectrum 422 in FIG. 4F1, with slightdifferences in color properties and levels of circadian stimulation, asshown in the table in FIG. 4F2.

In the case of a 465 nm peak Gaussian CSWR with a FWHM of 30 nm, it isillustrative to compare the relative CS for common light sources withLED white light sources provided by the present disclosure. FIG. 4Gshows the CS (normalized to that for CIE A) as a function of colortemperature for common light sources such as candlelight (1850K), CIE A(2856K), D50 phase daylight (5000K), and D65 phase daylight (6500K). TheCS varies from about 25% (candlelight) to almost four times (D65) thatof CIE A. Also plotted are the CS for a 455 nm blue primary LEDtwo-phosphor 3000K LED, and that for a 425 nm violet primary LEDtwo-phosphor 3000K LED. The difference in circadian stimulation isremarkable, with that for the 455 nm-based LED white light source beingmore than 1.5-times higher than that of CIE A, and more than three timesthat of the 425 nm-based LED white light source. It is worth noting thatCe³⁺ garnet phosphors (e.g., “YAG”) are not highly absorbing in theviolet, so for the 425 nm-based LED it may be desirable to use a Eu²⁺phosphor for the green, as well as for the red, emissions.

FIG. 4H shows light strip having two different sets of LED-basedemitters, and a clock/timer, control circuits 4H01, and a driver tocontrol the ratio of emissions of the two different sets of LED-basedemitters to implement a circadian-friendly LED white light source,according to some embodiments.

As shown, a first group of violet-primary LEDs with an appropriate mixof red-, green- and (optionally) blue-emitting phosphors 4H02 can becombined with a second group of violet-primary LEDs with blue phosphors,or blue-primary LEDs, 4H04.

The first and second groups of LED-based emitters may be contained inseparate packages, and the light combined with mixing optics, or theLED-based emitters may be incorporated into a single package, such as as chip-on-board (COB) package (e.g., see the arrangement of FIG. 8 )and/or linear COB packages. COB packages can be used in a lamp assemblyas is shown in FIG. 6A and FIG. 6B.

In addition, although the above embodiments describe two-channel tuningmethods to provide varying levels of circadian stimulation whilemaintaining a high quality of light, which can be useful to minimizecost and complexity, it is possible to use three or more channels usingthe devices and concepts provided disclosure. More channels offer moredegrees of freedom in terms of light source selection, and tuning forarbitrary (e.g., non-linear) curves in chromaticity space, but at thecost of higher levels of complexity in terms of luminaire design, LEDprocurement, mixing, and control.

In addition to the elements shown in FIG. 4H one or more light mixingoptics (not shown) may be used to mix the LED emissions first group andsecond group to provide a uniform or other desired light colorappearance. Still further, secondary optics can be used to achieve adesired light distribution pattern.

The foregoing discussion is focused on lighting systems and benefitsresulting from a reduced CS. However, display systems can also benefitfrom a reduced CS.

FIG. 4I shows measured SPDs 4100 for two display systems with a whitescreen—a laptop screen 402 and a smartphone screen 404. Examples ofother display systems are illustrated in FIGS. 15D1 through 15E2. Bothdisplays shown in FIG. 4I have CCTs of about 6500K, which is typical fordisplay screens. Both are lit by blue-primary LEDs and the emissionspectra are characterized by a large blue peak. The relative circadianstimulation is about 330% for the laptop and about 470% for the phonescreen.

FIG. 4J shows the predicted melatonin suppression 406 (after 90 minexposure to a white screen of a smartphone) versus luminance for thesmartphone screen. In practice, luminance levels for displays can behigh—one hundred to several hundreds of lux in some cases (for instanceif the device is held close to the face). Therefore, the net impact onthe circadian system can be significant and can disrupt sleep patterns,even for a relatively short exposure time.

For display applications, there are already software solutions that aimat reducing circadian disruption. For instance, software such as “f.lux”can adapt the CCT of the screen with time: during the day, the CCT isabout 6500K, but as the night falls the CCT is ‘warmed’ to about 3400K.

FIG. 4K shows an example of a spectrum emitted by a white screen usingthis software: curve 410 is for the standard emission (6500K) and curve408 is for the warmed emission (about 3400K nominally).

The reduction in CCT is beneficial because the relative circadianstimulation is less at lower CCT. Namely, the relative circadianstimulation is about 330% for the standard emission and about 210% forthe warmed screen (assuming equal luminance), relative to illuminant A.While this is an improvement, stimulation is still high for the warmedscreen due to the use of blue-pump LEDs. Also, it can be useful toreduce CS while still achieving the more typical electronic displaywhite center point (typically 6000K to 7000K).

Therefore, as with lighting systems, a careful choice of the emissionwavelength and profile of the primary LED and of the overall SPD isimportant to obtain a display system with a low circadian stimulation.

FIG. 4L1 illustrates relevant spectra for typical LED-lit liquid crystaldisplays (LCD), which are used in many applications includingtelevisions, monitors, laptop and notebook computers, gaming systems,and portable devices such as tablets, phones, MP3 players, etc. FIG. 4L1shows spectra for a blue color filter 412, a green color filter 414, anda red color filter 416 (collectively, CFs) which are employed inconjunction with an LCD display to control color. A typical LED spectrum(e.g., LED spectrum 418) is a blue primary-based LED pumping a yellow(and/or red) emitting phosphor system. Filtering by the red, green andblue filters results in a transmitted spectrum, for example, a whitetransmitted spectrum 419 if all three filters fully transmit. A typicalcolor gamut of this system (shown as triangle 426 in FIG. 4L2) islimited in the green and red, and covers an area in x-y chromaticityspace of about 79% with respect to the National Television SystemCommittee gamut standard 422 (NTSC, 1953). As discussed above, such anLED-based source (with a primary peak wavelength typically in the 440 nmto 460 nm range) is inherently highly circadian stimulating, which canbe undesirable especially for viewing in the evenings and nighttime.FIG. 4L2 also shows the Planckian locus 424 and the boundaries of the(xy) colorspace 420.

FIG. 4M shows the calculated relative CS (curve 430) and relativedisplay efficacy (curve 428) as the “blue” LED primary peak wavelengthis decreased (using the same phosphor emission, while maintaining thesame display white color point), using a 465 nm peak Gaussian CSWR witha FWHM of 30 nm. For peak wavelengths less than 440 nm, there is asignificant drop in CS, which reaches a minimum at about 410 nm. Theefficacy reduces also, but more slowly with decreasing peak wavelength,suggesting an optimum peak wavelength range between 410 nm and 440 nm orbetween 420 nm to 430 nm for a reduced-CS display.

FIG. 4N1 shows embodiments for which the phosphor system is tuned tobetter work with a chosen primary peak emission wavelength of 425 nm. InFIG. 4N1, 83% NTSC is achieved using phosphors with peak/FWHM (emission)of 530 nm/85 nm and 605 nm/80 nm, with only about a 10% efficacy penaltycompare to a 450 nm-based source achieving 79% NTSC. In FIG. 4N2, 90%NTSC is achieved using phosphors with peak/FWHM (emission) of 530 nm/85nm and 630 nm/80 nm, with only about a 20% efficacy penalty compare to a450 nm-based source achieving 79% NTSC. One skilled in the art canidentify different combinations of phosphors to achieve the desiredbalance of color gamut and efficacy. Use of a 425 nm wavelength primaryLED can reduce CS by about five times, which is extremely significant.Referring to FIG. 4J, a five times reduction for a 100 lux display wouldreduce melatonin suppression from about 50% to about 20% for a 90 minuteexposure.

Application of the present disclosure is not limited to displays basedon LCDs. Direct-view LED displays have been demonstrated, using bothorganic and inorganic LEDs. In these displays individual pixels are madeup of active LEDs, which include blue, green, and red emitters and areselectively controlled. Based on embodiments of the present disclosure,the “blue” emitters may be tuned to shorter wavelengths to reduce CS asdescribed. In certain embodiments, using a 465 nm peak Gaussian CSWRwith a FWHM of 30 nm, an optimum peak wavelength range for the “blue”emitter can be between 410 nm and 440 nm, more preferably between 420 nmand 30 nm, can be chosen for a reduced-CS display.

It is also possible to mix longer and shorter wavelength primary “blue”LEDs in order to have displays in which CS can be controlled. Forexample, it may be desirable to have high CS stimulation in the morning(e.g., 440 nm to 460 nm primary “blue”) that shifts to shorterwavelength (e.g., 420 nm to 430 nm) during the evening. This can be doneby including two sets of primary “blue” LEDs in the display and can beimplemented in both LCD and direct-view LED-based displays.

In some cases the color point (or more generally the spectrum) of theembodiments can be tuned automatically in response to behavior oractions of the end user. Examples of such trigger events include thepresence of the end user in a room (or a part of the room) for a givenamount of time, the movement of the user across the space, the user'sgeneral level of activity, specific words or gestures, and/or actions ona device (a smartphone for instance). Such responses may be employed tomatch the spectrum to the condition of the user (for instance, lower thecircadian cycle when the user becomes sleepy or prepares for sleep) orto modify the condition of the user (e.g., detect sleepiness andincrease circadian stimulation to lessen it). In some cases, theresponse can be determined by the user's behavior in combination withother measurable conditions or cues such as time of the day, weatherand/or changing weather, amount of outdoor light, etc. In some cases,the cues can be obtained from another “smart” system (another appliance,a smartphone, or other electronic device) which monitors the user'sbehavior—the cues can then be communicated over a network (wired orwireless) between said smart system and the lighting system, such as anetwork enabled by a smart-home hub. In some cases the cues relate tothe user's past behavior, such as the time the user woke up or his pastsleep pattern, which has been recorded by a system such as the user'ssmart phone.

In some cases, a response can be predetermined by the manufacturer ofthe system so that a given set of cues leads to a deterministicresponse. In other cases, the lighting system “learns” from the user.For instance, in a teaching phase, the user (or another person) manuallytunes the spectrum. The system learns to associate these settings withspecific cues and the tuning is then performed automatically in responseto the cues, (e.g., rather than being triggered manually). Learning canbe achieved by a variety of machine-learning techniques known to thoseskilled in the art, such as via a neural network and/or using Bayesianinference.

A specific example of the previous scenario is as follows: The userfollows a routine (e.g., a series of actions performed repeatedly withsome periodicity) a few hours before going to bed. Such a routine mightinclude leaving the dining table, brushing his teeth, watching TV etc.Cues of this routine are collected by various appliances (TV,toothbrush, motion sensors) and communicated with the lighting systemthrough a wireless protocol. In the teaching phase, the user also tunesthe spectrum of the lighting system to reduce circadian stimulation—forexample, the user the lighting system to a non-stimulating setting a fewhours before going to bed. Once the system has associated these settingswith one or more cues of the routine, and with an approximate hour, thetuning occurs automatically to help reduce the circadian response beforethe user goes to bed. Conversely, tuning can also occur in the morningto stimulate the circadian system.

Such automated behavior can be used for a variety of light-emittingsystems—including lighting appliances per se, and for display systems(e.g., TV and computer screens, tablets, phones, etc.). Such lightingsystems may for instance adapt their spectrum to reduce circadianstimulation a given time before the user goes to bed. In the case ofdisplay systems, the change in LED spectrum may be combined withsoftware changes (such as the screen's color point) in order to furtherreduce circadian stimulation. Such automated behavior can be implementedin a wide variety of lighting situations. Strictly as one example, alight strip can be fitted with sensors to take-in and/or learn frommeasurable aspects and/or changes in the environment, and in response,tune circadian-friendly emissions.

While the previous examples assumed a domestic setting, such embodimentswith automatic or ‘smart’ tuning can be used in other contexts such asin a professional context. For example, in an office setting, thelighting system may adapt to monitor used activity and increase CSaccordingly; or the CS may be increased in the morning, reduced near theend of the work day, or adapted to complement the outside lightingconditions (which could vary with weather and season). System tuning mayfollow a simple timing scheme or also take into account the workers'behavior. Embodiments may also be used in other contexts where sleeppattern is affected, including night-shift worker facilities, long-rangetravel (such as airplane flights), care facilities for the elderly.

Further, in various cases, the intensity of the light emitted by thesystem may be tuned together with its spectrum to further influence CS.For instance, the intensity may be dimmed as the spectrum is tuned forlower CS. In the case of a display, the luminance of the display may bedimmed and its CS may be lowered if the ambient light in the roomdecreases—this can be detected by a simple light sensor connected to thedisplay.

FIG. 5A is a chart 5A00 showing a linear chromaticity curve 502 producedby a circadian-friendly LED white light source in x-y chromaticityspace. FIG. 5A also shows the Planckian loci 510 and minimum-hue-shiftcurve 512 as described by Rea and Freyssinier, Color Research andApplication 38, 82-92 (2013).

The Planckian loci form a curve in chromaticity space, leading to thepopular notion that a linear dual-track tunability cannot properlyreplicate white emission across a wide range of color temperatures.However, recent psychophysical experiments show that the definition of“white” may deviate from the Planckian curve. In particular, subjectstend to observe less tint for color points below the Planckian loci.

This observation has two ramifications: 1) a person's perception of“white” is somewhat arbitrary, and 2) tinting below the Planckian curvemay not only be acceptable, but perhaps preferred. Opening up thisregion in chromaticity space allows for the engineering of dual-channeltunable white emission. The chromaticities for the three colortemperatures described for a circadian friendly light-source (FIG. 2A)are shown (e.g., see point 504, point 506, and point 508) superimposedon the Planckian loci and the “minimum-hue-shift” points. Based on thearguments above, these three color points (and those in between) canprovide an acceptable white appearance, as well as good color renderingproperties.

Again this is not trivial to achieve because the most obvious way toreduce the CS of a light source is to remove blue or cyan light, thusshifting the chromaticity above the Planckian (and away from thepreferred chromaticity curve 502 shown in FIG. 5A).

FIG. 5B is a chart 5B00 showing the shape of a white light boundingregion 514 as produced by a circadian-friendly LED white light source,according to some embodiments. The white light bounding region 514 istaken as the range limits of the Planckian loci 510 and“minimum-hue-shift” curves, inclusive of a ±0.005 border region in x-ychromaticity space.

As shown in FIG. 5B, the white light bounding region is highlighted withhatching. In particular, the hatched region 514 represents varyingratios of color mixing, and bounds of a white light region.

In yet other embodiments, the change in circadian stimulation is notassociated with a change in CCT or chromaticity. This can be useful insituations for which a given CCT (e.g., 3000K or 6500K) is desired atall times, but the stimulation should vary through the day. This can beuseful for lighting applications and for display applications, where CSmay be changed without the user being aware in a change in illumination.Such embodiments may, for example, be achieved by combining twoLED-based tracks emitting light with a CCT of 3000K. One track can havea large relative circadian stimulation, and the other can have a lowcircadian stimulation. More specifically, the first track may includeblue pump LEDs and phosphors and the second track may include violetLEDs and phosphors. As disclosed herein, the emission spectrum from eachtrack can also be designed to provide high quality of light (e.g., a CRIabove 80). In such systems, it may be desirable to design the spectrasuch than their chromaticities are similar perceptually rather thannominally. Alternatively, it may be desirable to compute thechromaticities with suitable color matching functions (CMFs) such as the1964 CMFs or other modern CMFs, rather than the conventional 1931 2degree CMFs. This is because the predictions of the 1931 2 degree CMFsare sometimes poorly representative of user perception. In addition,chromaticity calculations may be performed for a given demographic group(e.g., taking into account the reduction of sensitivity toshort-wavelength light for elderly users).

Such embodiments, with a stable CCT, are illustrated in FIG. 5C1 throughFIG. 5C4, in which two sets of LED-based sources are controlledindependently: 1) a blue primary based LED white source at 3300K withCRI about 80 and R9 greater than 0 (“BLED” 502), and 2) a violet primarybased LED white source at 3300K with CRI about 80 and R9 greater than 0(“VLED” 504). When the BLED devices are on and the VLED off, thecircadian stimulation is high (210% of CIE A). Alternatively, When theVLED devices are on and the BLED off, the circadian stimulation is low(54% of CIE A). In mixed combinations, the circadian stimulation variesbetween these two levels; however, the chromaticity is nominallyunchanged. In other embodiments the primary blue LEDs could be replacedby blue phosphors pumped by shorter wavelength LEDs. FIG. 5C2 shows theCIE 508 for an LED-based white light source described above and FIG. 5C3shows an example of the combined VLED and BLED spectrum 506. The CS forrepresentative BLED fractions is provided in FIG. 5C4.

Here again, the change in CS can also be related to a change in relativespectral content (e.g., fraction of the SPD) Fv in the ‘violet-blue’(VB) range 400 nm to 440 nm and Fc in the ‘blue-cyan’ (BC) range 440 nmto 500 nm. Referring to FIG. 5C1, for SPD 502, Fv=0.01 and Fc=0.14 andfor SPD 504 Fv=0.24 and Fc=0.05.

In certain embodiments, an LED emission source is characterized by acolor rendering index above 80; a Fv of at least 0.01, at least 0.05, atleast 0.1, at least 0.15, at least 0.2, and in certain embodiments, atleast 0.25; and an Fc of at least 0.01, at least 0.05, at least 0.1, atleast 0.15 at least 0.2, at least 0.25, at most 0.01, at most 0.05, atmost 0.10, at most 0.15, at most 0.20 or at most 0.25; or a combinationof any of the foregoing.

FIG. 6A shows an exploded view 6A00 and FIG. 6B shows an assembly view6B00 of a LED lamp forming a circadian-friendly LED light source.

As shown in FIG. 6A and FIG. 6B, the exploded view 6A00 includes a GU10(10 mm “twist-lock”) base for connecting to a 120/230-volt source. Suchan embodiment can be used as an MR16 halogen light replacement 6B00 forthe 35/50 watt halogen lamps in use since the mid-2000s.

The lamp shown in FIG. 6A and FIG. 6B is merely one embodiment of a lampthat conforms to fit with any one or more of a set of mechanical andelectrical standards.

The list above is representative and is not intended to include all thestandards or form factors that may be utilized with embodimentsdescribed herein.

FIG. 7 shows a schematic of a multi-track driver control system as usedin an LED lamp employing a circadian-friendly LED light source. As shownin FIG. 7 , the emission of multiple strings of LEDs is separatelyvaried such that the ratio of output of one string with respect toanother string is varied according to a time-based function. Forexample, the clock/timer can model the sunrise and sunset timings over a24-hour period, and during the 24 hour period, a violet emitting LEDwith blue phosphor can be attenuated in afternoon and evening hours. Indual track systems, a linear chromaticity curve 502 can be implemented.With three or more tracks (e.g., the shown three groups of LEDs)non-linear chromaticity curves can be enabled. Suitable driver controlsystems are disclosed in U.S. Application No. 62/026,899 filed on Jun.25, 2014, which is incorporated by reference in its entirety.

Control circuits (e.g., control modules) can employ any known-in-the-arttechniques, including current limiting based on current or voltagesensing, and/or current limiting based on temperature sensing. Morespecifically, one or more current limiters (e.g., current limiter 704)can be controlled by any known techniques. The controller and/or currentlimiters in turn can modulate the current flowing to any individualgroups of LEDs (e.g., Group1 LEDs 706, Group2 LEDs 708, GroupN LEDs 709,

etc.), which current flowing to any individual groups can beindividually increased or decreased using FETs or switches (e.g., SW1710, SW2 712, SW3 714, etc.). The shown control circuits 719 compriseenvironmental sensors, and a clock/timer, each of which provide inputsto controller 721, which in turn serves to modulate the current flowingto any individual groups of LEDs (e.g., Group1 LEDs 706, Group2 LEDs708, GroupN LEDs 709, etc.).

FIG. 8 shows two strings of LEDs in an intermixed physical arrangement802 to form a two-channel, circadian-friendly arrangement 800 as used inan LED lamp. As shown, the control circuits can employ anyknown-in-the-art techniques to independently modulate the currentflowing to either of the shown groups of LEDs (e.g., Group1 LEDs 706,Group2 LEDs 708).

Each of the Group1 LEDs, and Group2 LEDs comprise individualpatterned-phosphor chips so that the circadian-friendly source may becondensed into a compact area, for example, for directional lighting. Amixing optic can be included to mix the two types of LED light emissions(e.g., for homogeneity). The arrangement shown is illustrative and otherarrangements are suitable. Techniques for patterning phosphors aredisclosed in U.S. application Ser. No. 14/135,098, filed on Dec. 19,2013, which is incorporated by reference in its entirety.

FIG. 9A presents a selection of lamp shapes corresponding toknown-in-the-art standards. The aforementioned lamps are merely selectedembodiments of lamps that conform to fit with any one or more of a setof mechanical and electrical standards. Table 1 gives standards (see“Designation”) and corresponding characteristics.

TABLE 1 Base Diameter IEC 60061-1 Designation (Crest of thread) NameStandard Sheet E05 05 mm Lilliput Edison Screw (LES) 7004-25 E10 10 mmMiniature Edison Screw (MES) 7004-22 E11 11 mm Mini-Candelabra EdisonScrew (mini-can) (7004-06-1) E12 12 mm Candelabra Edison Screw (CES)7004-28 E14 14 mm Small Edison Screw (SES) 7004-23 E17 17 mmIntermediate Edison Screw (IES) 7004-26 E26 26 mm [Medium] (one-inch)Edison Screw (ES or MES) 7004-21A-2 E27 27 mm [Medium] Edison Screw (ES)7004-21 E29 29 mm [Admedium] Edison Screw (ES) E39 39 mm Single-contact(Mogul) Giant Edison Screw (GES) 7004-24-A1 E40 40 mm (Mogul) GiantEdison Screw (GES) 7004-24

Additionally, the base member of a lamp can be of any form factorconfigured to support electrical connections, which electricalconnections can conform to any of a set of types or standards. Forexample Table 2 gives standards (see “Type”) and correspondingcharacteristics, including mechanical spacing between a first pin (e.g.,a power pin) and a second pin (e.g., a ground pin).

TABLE 2 Pin center Pin Type Standard to center Diameter Usage G4 IEC60061-1 4.0 mm 0.65-0.75 mm MR11 and other small halogens of (7004-72)5/10/20 watt and 6/12 volt GU4 IEC 60061-1 4.0 mm 0.95-1.05 mm(7004-108) GY4 IEC 60061-1 4.0 mm 0.65-0.75 mm (7004-72A) GZ4 IEC60061-1 4.0 mm 0.95-1.05 mm (7004-64) G5 IEC 60061-1 5 mm T4 and T5fluorescent tubes (7004-52-5) G5.3 IEC 60061-1 5.33 mm 1.47-1.65 mm(7004-73) G5.3-4.8 IEC 60061-1 (7004-126-1) GU5.3 IEC 60061-1 5.33 mm1.45-1.6 mm (7004-109) GX5.3 IEC 60061-1 5.33 mm 1.45-1.6 mm MR16 andother small halogens of (7004-73A) 20/35/50 watt and 12/24 volt GY5.3IEC 60061-1 5.33 mm (7004-73B) G6.35 IEC 60061-1 6.35 mm 0.95-1.05 mm(7004-59) GX6.35 IEC 60061-1 6.35 mm 0.95-1.05 mm (7004-59) GY6.35 IEC60061-1 6.35 mm 1.2-1.3 mm Halogen 100 W 120 V (7004-59) GZ6.35 IEC60061-1 6.35 mm 0.95-1.05 mm (7004-59A) G8 8.0 mm Halogen 100 W 120 VGY8.6 8.6 mm Halogen 100 W 120 V G9 IEC 60061-1 9.0 mm Halogen 120 V(US)/230 V (EU) (7004-129) G9.5 9.5 mm 3.10-3.25 mm Common for theatreuse, several variants GU10 10 mm Twist-lock 120/230-volt MR16 halogenlighting of 35/50 watt, since mid-2000s G12 12.0 mm 2.35 mm Used intheatre and single-end metal halide lamps G13 12.7 mm T8 and T12fluorescent tubes G23 23 mm 2 mm GU24 24 mm Twist-lock forself-ballasted compact fluorescents, since 2000s G38 38 mm Mostly usedfor high-wattage theatre lamps GX53 53 mm Twist-lock for puck-shapedunder-cabinet compact fluorescents, since 2000s

The list above is representative and should not be taken to include allthe standards or form factors that may be utilized within embodimentsdescribed herein.

FIG. 9B through FIG. 9I present selections of troffers corresponding tovarious shapes (e.g., substantially square, substantially rectangular)and installation configurations (e.g., recessed, flush mounted, hanging,etc.). Combinations of the foregoing multi-track driver control system(see FIG. 7 ), and strings of LEDs in an intermixed physical arrangement(see FIG. 8 ) can be used with the exemplary troffers and/or with anysorts of general illumination fixtures.

Other luminaires such as suspended luminaires may emit light upwardrather than downward, or may emit light in both directions.

FIG. 10A through FIG. 10I depict embodiments of the present disclosurein the form of lamp applications. In these lamp applications, one ormore light emitting diodes are used in lamps and fixtures. Such lampsand fixtures include replacement and/or retro-fit directional lightingfixtures.

In some embodiments, aspects of the present disclosure can be used in anassembly. As shown in FIG. 10A, the assembly comprises:

-   -   a screw cap 1028    -   a driver housing 1026    -   a driver board 1024    -   a heatsink 1022    -   a metal-core printed circuit board 1020    -   an LED light source 1018    -   a dust shield 1016    -   a lens 1014    -   a reflector disc 1012    -   a magnet 1010    -   a magnet cap 1008    -   a trim ring 1006    -   a first accessory 1004    -   a second accessory 1002

The components of assembly 10A00 may be described in substantial detail.Some components are ‘active components’ and some are ‘passive’components, and can be variously-described based on the particularcomponent's impact to the overall design, and/or impact(s) to theobjective optimization function. A component can be described using aCAD/CAM drawing or model, and the CAD/CAM model can be analyzed so as toextract figures of merit as may pertain to e particular component'simpact to the overall design, and/or impact(s) to the objectiveoptimization function. Strictly as one example, a CAD/CAM model of atrim ring is provided in a model corresponding to the drawing of FIG.10A2.

The components of the assembly 10B100 and assembly 10B200 can be fittedtogether to form a lamp. FIG. 10B1 depicts a perspective view 1030 andFIG. 10B2 depicts a top view 1032 of such a lamp. As shown in FIG. 10B1and FIG. 10B2, the lamp 10B100 and 10B200 comports to a form factorknown as PAR30L. The PAR30L form factor is further depicted by theprincipal views (e.g., left 1040, right 1036, back 1034, front 1038 andtop 1042) given in array 10C00 of FIG. 10C.

The components of the assembly 10D100 and assembly 10D200 can be fittedtogether to form a lamp. FIG. 10D1 depicts a perspective view 1044 andFIG. 10D2 depicts a top view 1046 of such a lamp. As shown in FIG. 10D1and in FIG. 10D2, the lamp 10D100 and 10D200 comports to a form factorknown as PAR30S. The PAR30S form factor is further depicted by theprincipal views (e.g., left 1054, right 1050, back 1048, front 1052 andtop 1056) given in array 10E00 of FIG. 10E.

The components of the assembly 10A00 can be fitted together to form alamp. FIG. 10F1 depicts a perspective view 1058 and FIG. 10F2 depicts atop view 1060 of such a lamp. As shown in FIG. 10F1 and FIG. 10F2, thelamp 10F100 and 10F200 comports to a form factor known as PAR38. ThePAR38 form factor is further depicted by the principal views (e.g., left1068, right 1064, back 1062, front 1066 and top 1070) given in array10G00 of FIG. 10G.

The components of the assembly 10A00 can be fitted together to form alamp. FIG. 10H1 depicts a perspective view 1072 and FIG. 10H2 depicts atop view 1074 of such a lamp. As shown in FIG. 10H1 and FIG. 10H2, thelamp 10H100 and 10H200 comports to a form factor known as PAR111. ThePAR111 form factor is further depicted by the principal views (e.g.,left 1082, right 1078, back 1076, front 1080 and top 1084) given inarray 10100 of FIG. 10I.

In addition to uses of the aforementioned lamps and lamp shapes, filtersor so-called ‘circadian phosphors’ can be employed.

Using Filters or Phosphors

Various implementations can be considered to alter an SPD's impact onthe circadian system. As discussed above, it is possible to use amultiple-channel system including violet-pump and blue-pump LEDs and tobalance the contribution of both channels. Besides, it is possible tophysically block a given spectral range (such as the blue, cyan orviolet region)—for instance by using absorbing or reflecting filterswhich may be fixed or moving. Filters offer the advantage that asubstantial amount of light (or even all the light) can be blocked in agiven spectral range, which may be of importance. For instance, it maybe desirable to block nearly all the light in the blue-cyan range (or ina more specific range) to obtain a very low circadian stimulation—thisis because standard spectra (such as a dimmed filament lamp) still havea fair amount of circadian stimulation. Such filters may for instance bedichroic reflective filters or absorbing filters including dye filtersin a matrix (glass, plastic or other)

Another option, however, is to use a light-converting material in thesystem with a carefully chosen absorption range. For instance, one mayinclude a phosphor which absorbs blue light and down-converts it togreen or red light. This approach may be desirable because it enablesone to remove a substantial amount of light in the absorption range likea blocking approach would, but with higher system efficiency since theradiation is converted to another wavelength rather than merely beingblocked. For simplicity, we call this phosphor the ‘circadian phosphor’,since its absorption has an impact on the circadian action of the lightsource.

FIG. 11A and FIG. 11B contrasts the two approaches. FIG. 11A shows theinitial SPD of a white LED source 1101, and the filtered SPD 1102 afterblue light is blocked by a filter. The filtered SPD 1102 can be used inmany embodiments, as it has a low amount of blue light, which can reducedisruption of the circadian system; furthermore the width and generalshape of the filter may be designed to control this effect. However,filtering induces a penalty in efficiency because the filtered light islost.

FIG. 11B shows the initial SPD of a white LED source 1103, and theconverted SPD 1104 after blue light is absorbed by a “circadianphosphor” and converted to yellow light 1105. In this case, the samedesirable effect on the circadian system is obtained, but the impact onefficiency is lessened thanks to the conversion of blue light. Hereagain, various aspects of the approach can be controlled through design,such as the position and amplitude of the absorption dip, whichabsorption dip can be controlled through the choice and amount ofphosphor, and the position and amplitude of the luminescence. Forinstance, the absorption may be chosen to substantially block blue lightbut to allow some violet light transmission.

The circadian phosphor may be static, in which case the emitted SPD doesnot vary, or it may be on a moving part in order to control the SPDdynamically. The moving part may be a plate containing the phosphor,which can be moved mechanically in and out of the path of light emissionof the system.

In FIG. 11A and FIG. 11B, the embodiments are designed to remove lightin the range 440 nm to 460 nm. By choosing other filters or otherphosphors this range can be tuned—for instance the range 450 nm to 480nm, or another range, can be targeted and the spectral power in therange reduced. In some embodiments, a specific circadian action spectrumis assumed and the SPD is designed to have a low amount of light in therange where the action spectrum is high.

In yet another embodiment, the circadian phosphor shows a saturationbehavior: it absorbs light at low flux, but absorption saturates at highflux. Such an approach is illustrated in FIG. 12 through FIG. 14 .

FIG. 12 shows various spectra. Spectrum 1201 is an emission spectrum ofa white LED source with a CCT of 3000K and a CRI of about 90. Thisspectrum may be obtained by combining a violet-pump LED and severalphosphors (e.g., a green phosphor, a red phosphor and possibly a bluephosphor). Curve 1202 is the absorption spectrum of a saturable redcircadian phosphor and curve 1203 is the corresponding luminescencespectrum. Spectrum 1202 and spectrum 1203 can be obtained, for instance,with Mn-doped phosphors such as K₂[TiF₆]:Mn⁴⁺.

FIG. 13 shows a possible way to combine such a white LED source and sucha saturable phosphor. In FIG. 13 , the saturable circadian phosphor 1302is placed above the LED source 1301 so that the white light emitted bythe device 1303 can be absorbed by the circadian phosphor. Various otherconfigurations are also possible—for instance, the circadian phosphormay be mixed with the phosphors of the white LED or may be in a remoteconfiguration.

FIG. 14A and FIG. 14B show the resulting spectral and colorimetricproperties of the system shown in FIG. 13 . FIG. 14A shows the spectrumemitted by the system at various LED drive currents. At low drivecurrent the saturable phosphor is not saturated and absorbs most of thelight in its absorption range (e.g., blue-cyan light), resulting inspectrum 1401. At higher drive current the phosphor absorption ispartially saturated and part of the blue-cyan light is transmitted,resulting in spectrum 1402. At even higher drive current the phosphorabsorption is fully saturated, and the original spectrum of the whiteLED 1403 is emitted with very little perturbation from the circadianphosphor. FIG. 14B shows the corresponding chromaticity in (x, y) spacefor each drive current. At low drive current the CCT is about 2000K1405, at higher drive current it is about 2500K 1406 and at the highestdrive current it is about 3000K 1407. In all cases, the chromaticity isclose to the Planckian locus 1404.

The embodiments of FIG. 12 through FIG. 14 achieve several desirableproperties. At high drive current (e.g., see curve 1402), theembodiments behave like a conventional halogen retrofit with a high CRI(e.g., the circadian stimulation is 128% relative to standard illuminantA). As the current is reduced (e.g., see curves 1403 and 1401), thechromaticity shifts toward lower CCT (from 1407 to 1406 to 1405) thusemulating the behavior of a dimmed halogen or incandescent lamp. Inaddition, the spectrum is modified so that circadian stimulationdecreases; at the lowest drive condition there is very little radiationin the range 440 nm to 490 nm (e.g., see curve 1401) and therefore verylow stimulation of the circadian system (the circadian stimulation isonly 8% relative to standard illuminant A).

As in other embodiments, the properties of the SPDs shown in FIG. 14Acan be characterized by their relative fraction of power Fv in the range400 nm to 440 nm and the fraction of power Fc in the range 440 nm to 500nm. For SPD 1401, Fv=0.06 and Fc=0.01; for SPD 1402, Fv=0.08 andFc=0.12. The value of Fc is especially low for SPD 1401, which can beassociated with a very low circadian stimulation. This is in contrast totypical LED sources where a substantial fraction of power is in therange 440 nm to 500 nm (even for low-CCT sources with a CCT below2700K).

While sources of varying CCT are known in the art and can be useful tomodulate circadian stimulation, this embodiment has superior properties.The circadian stimulation is extremely low at low drive conditions: itis indeed lower than what is achieved with conventional LED sources,which employ a blue pump LED, or even by dimming of a conventionalincandescent/halogen lamp. For example, a dimmed filament lamp emittinga blackbody spectrum with a CCT of 2000K still has a circadianstimulation of about 54% relative to illuminant A. Furthermore thepresent embodiment is ‘passive’ in that it doesn't require multiplechannel drivers to modulate the spectrum. Therefore, such an embodimentmay be integrated to a retrofit lamp or more generally a lighting systemin absence of any advanced control circuits. In some such cases standarddimming switches provides the needed control.

In this embodiment, the presence of a violet pump is of importance sincethe violet light enables the chromaticity to be near-Planckian at lowdrive current, even in the absence of blue-cyan light.

Various aspects of this embodiment can be advantageously controlled. Forinstance, the optical properties of the pump LED can be varied, and theselection of phosphors can be varied, and the relative loading ofphosphors can be varied to accomplish an optimization objective. Theoptimization criteria may include the CRI of the source at variousdimming levels, its chromaticity and various dimming level, and metricsrelated to its circadian impact at various dimming levels. Strictly asone example, optimization criteria may include aspects of an integratedcircadian action spectrum. The loading of the circadian phosphor can bechosen so that its saturation occurs at a desired drive, such as, forinstance, 10% dimming. In other embodiments, more than one circadianphosphor is used.

In other embodiment, the white LED is obtained by multiple LED chips,such as uses of a violet LED, a green LED and a red LED rather than aphosphor-converted LED. In other embodiments, the chromaticity of thesource does not follow the Planckian locus—it may for instance be belowthe Planckian locus, which is sometimes associated with a preferredperception as already discussed.

Embodiments may be integrated to various systems. This includes lightingsystems (e.g., lamps, troffers and others) and non-lighting systems(e.g., display applications).

FIG. 15A1 through FIG. 15I depict embodiments of the present disclosureas can be applied toward lighting applications. In these embodiments, asshown in FIGS. 15A1-15A3, one or more light-emitting diodes 15A10, astaught by this disclosure, can be mounted on a submount or package toprovide an electrical interconnection. As shown in FIGS. 15B1-15B3 asubmount or package can be a ceramic, oxide, nitride, semiconductor,metal, or combination thereof that includes an electricalinterconnection capability 15A20 for the various LEDs. The submount orpackage can be mounted to a heatsink member 15B50 via a thermalinterface. The LEDs can be configured to produce a desired emissionspectrum, either by mixing primary emissions from various LEDs, or byhaving the LEDs photo-excite wavelength down-conversion materials suchas phosphors, semiconductors, or semiconductor nanoparticles (“quantumdots”), or a combination of any of the foregoing.

The total light emitting surface (LES) of the LEDs and anydown-conversion materials can form a light source 15A30. One or morelight sources can be interconnected into an array 15B20, which in turnis in electrical contact with connectors 15B10 and brought into anassembly 15B30. One or more lens elements 15B40 can be optically coupledto the light source. The lens design and properties can be selected sothat the desired directional beam pattern for a lighting product isachieved for a given LES. The directional lighting product may be an LEDmodule, a retrofit lamp 15B70, or a lighting fixture 15C30. In the caseof a retrofit lamp, an electronic driver can be provided with asurrounding member 15B60, the driver to condition electrical power froman external source to render it suitable for the LED light source. Thedriver can be integrated into the retrofit lamp. In the case of afixture, an electronic driver is provided which conditions electricalpower from an external source to make it suitable for the LED lightsource, with the driver either integrated into the fixture or providedexternally to the fixture. In the case of a module, an electronic drivercan be provided to condition electrical power from an external source torender it suitable for the LED light source, with the driver eitherintegrated into the module or provided externally to the module.Examples of suitable external power sources include mains AC (e.g., 120Vrms AC or 240 Vrms AC), low-voltage AC (e.g., 12 VAC), and low-voltageDC (e.g., 12 VDC). In the case of retrofit lamps, the entire lightingproduct may be designed to fit standard form factors (e.g., ANSI formfactors). Examples of retrofit lamp products include LED-based MR16,PAR16, PAR20, PAR30, PAR38, BR30, A19 and various other lamp types.Examples of fixtures include replacements for halogen-based and ceramicmetal halide-based directional lighting fixtures.

In some embodiments, the present disclosure can be applied tonon-directional lighting applications. In these embodiments, one or morelight-emitting diodes (LEDs), as taught by the disclosure, can bemounted on a submount or package to provide an electricalinterconnection. The submount or package can be, for example, a ceramic,oxide, nitride, semiconductor, metal, or combination of any of theforegoing that includes electrical interconnection capability for thevarious LEDs. The submount or package can be mounted to a heatsinkmember via a thermal interface. The LEDs can be configured to produce adesired emission spectrum, either by mixing primary emissions fromvarious LEDs, or by having the LEDs photo-excite wavelengthdown-conversion materials such as phosphors, semiconductors, orsemiconductor nanoparticles (“quantum dots”), or a combination thereof.The LEDs can be distributed to provide a desired shape of the lightsource. For example, one common shape is a linear light source forreplacement of conventional fluorescent linear tube lamps. One or moreoptical elements can be coupled to the LEDs to provide a desirednon-directional light distribution. The non-directional lighting productmay be an LED module, a retrofit lamp, or a lighting fixture. In thecase of a retrofit lamp, an electronic driver can be provided tocondition electrical power from an external source to render it suitablefor the LED light source, with the driver integrated into the retrofitlamp. In the case of a fixture, an electronic driver is provided tocondition electrical power from an external source to render it suitablefor the LED light source, with the driver either integrated into thefixture or provided externally to the fixture. In the case of a module,an electronic driver can be provided to condition electrical power froman external source to render it suitable for the LED light source, withthe driver either integrated into the module or provided externally tothe module. Examples of external power sources include mains AC (e.g.,120 Vrms AC or 240 Vrms AC), low-voltage AC (e.g., 12 VAC), andlow-voltage DC (e.g., 12 VDC). In the case of retrofit lamps, the entirelighting product may be designed to fit standard form factors (e.g.,ANSI form factors). Examples of non-directional lighting products areshown in FIG. 15C1, FIG. 15C2, and FIG. 15C3. Such a lighting fixturecan include replacements for fluorescent-based troffer luminaires 15C30.In this embodiment, LEDs are mechanically secured into a package 15C10,and multiple packages are arranged into a suitable shape such as lineararray 15C20.

Some embodiments of the present disclosure can be applied tobacklighting for flat panel display applications. In these embodiments,one or more light-emitting diodes (LEDs), as taught by this disclosure,can be mounted on a submount or package to provide an electricalinterconnection. The submount or package can be a ceramic, oxide,nitride, semiconductor, metal, or combination of any of the foregoingthat include electrical interconnection capability for the various LEDs.The submount or package can be mounted to a heatsink member via athermal interface. The LEDs can be configured to produce a desiredemission spectrum, either by mixing primary emissions from various LEDs,or by having the LEDs photo-excite wavelength down-conversion materialssuch as phosphors, semiconductors, or semiconductor nanoparticles(“quantum dots”), or a combination of any of the foregoing. The LEDs canbe distributed to provide a desired shape of the light source. Onecommon shape is a linear light source. The light source can be opticallycoupled to a lightguide for the backlight. This can be achieved bycoupling at the edge of the lightguide (edge-lit), or by coupling lightfrom behind the lightguide (direct-lit). The lightguide distributeslight uniformly toward a controllable display such as a liquid crystaldisplay (LCD) panel. The display converts the LED light into desiredimages based on electrical control of light transmission and its color.One way to control the color is by use of filters (e.g., color filtersubstrate 15D40). Alternatively, multiple LEDs may be used and driven inpulsed mode to sequence the desired primary emission colors (e.g., usinga red LED 15D30, a green LED 15D10, and a blue LED 15D20). Optionalbrightness-enhancing films may be included in the backlight “stack”. Thebrightness-enhancing films narrow the flat panel display emission toincrease brightness at the expense of the observer-viewing angle. Anelectronic driver can be provided to condition electrical power from anexternal source to render it suitable for the LED light source forbacklighting, including any color sequencing or brightness variation perLED location (e.g., one-dimensional or two-dimensional dimming).Examples of external power sources include mains AC (e.g., 120 Vrms ACor 240 Vrms AC), low-voltage AC (e.g., 12 VAC), and low-voltage DC(e.g., 12 VDC). Examples of backlighting products are shown in FIG.15D1, FIG. 15D2, FIG. 15E1 and FIG. 15E2.

Some embodiments of the present disclosure can be applied to automotiveforward lighting applications, as shown in FIGS. 15F1-15F (e.g., see theexample of an automotive forward lighting product 15F30). In theseembodiments, one or more light-emitting diodes (LEDs) can be mounted ona submount or on a rigid or semi-rigid package 15F10 to provide anelectrical interconnection. The submount or package can be a ceramic,oxide, nitride, semiconductor, metal, or combination thereof, thatinclude electrical interconnection capability for the various LEDs. Thesubmount or package can be mounted to a heatsink member via a thermalinterface. The LEDs can be configured to produce a desired emissionspectrum, either by mixing primary emission from various LEDs, or byhaving the LEDs photo-excite wavelength down-conversion materials suchas phosphors, semiconductors, or semiconductor nanoparticles (“quantumdots”), or a combination of any of the foregoing. The total lightemitting surface (LES) of the LEDs and any down-conversion materialsform a light source. One or more lens elements 15F20 can be opticallycoupled to the light source. The lens design and properties can beselected to produce a desired directional beam pattern for an automotiveforward lighting application for a given LED. An electronic driver canbe provided to condition electrical power from an external source torender it suitable for the LED light source. Power sources forautomotive applications include low-voltage DC (e.g., 12 VDC). An LEDlight source may perform a high-beam function, a low-beam function, aside-beam function, or any combination thereof.

Certain embodiments of the present disclosure can be applied to digitalimaging applications such as illumination for mobile phone and digitalstill cameras (e.g., see FIGS. 15G1-15G4). In these embodiments, one ormore light-emitting diodes (LEDs), as taught by the disclosure, can bemounted on a submount or package 15G10 to provide an electricalinterconnection. The submount or package can be, for example, a ceramic,oxide, nitride, semiconductor, metal, or combination of any of theforegoing that include electrical interconnection capability for thevarious LEDs. The submount or package can be mounted to a circuit boardmember and fitted with or into a mounting package 15G20. The LEDs can beconfigured to produce a desired emission spectrum, either by mixingprimary emission from various LEDs, or by having the LEDs photo-excitewavelength down-conversion materials such as phosphors, semiconductors,or semiconductor nanoparticles (“quantum dots”), or a combinationthereof. The total light emitting surface (LES) of the LEDs and anydown-conversion materials form a light source. One or more lens elementscan be optically coupled to the light source. The lens design andproperties can be selected so that the desired directional beam patternfor an imaging application is achieved for a given LES. An electronicdriver can be provided to condition electrical power from an externalsource to render it suitable for the LED light source. Examples ofsuitable external power sources for imaging applications includelow-voltage DC (e.g., 5 VDC). An LED light source may perform alow-intensity function 15G30, a high-intensity function 15G40, or anycombination thereof.

Some embodiments of the present disclosure can be applied to mobileterminal applications. FIG. 15H is a diagram illustrating a mobileterminal (see smart phone architecture 15H00). As shown, the smart phone15H06 includes a housing, display screen, and interface device, whichmay include a button, microphone, and/or touch screen. In certainembodiments, a phone has a high resolution camera device, which can beused in various modes. An example of a smart phone can be an iPhone fromApple Inc. of Cupertino, Calif. Alternatively, a smart phone can be aGalaxy from Samsung, or others.

In an example, the smart phone may include one or more of the followingfeatures (which are found in an iPhone 4 from Apple Inc., although therecan be variations), see www.apple.com:

-   -   GSM model: UMTS/HSDPA/HSUPA (850, 900, 1900, 2100 MHz); GSM/EDGE        (850, 900, 1800, 1900 MHz)    -   CDMA model: CDMA EV-DO Rev. A (800, 1900 MHz)    -   802.11b/g/n Wi-Fi (802.11n 2.4 GHz only)    -   Bluetooth 2.1+EDR wireless technology    -   Assisted GPS    -   Digital compass    -   Wi-Fi    -   Cellular    -   Retina display    -   3.5-inch (diagonal) widescreen multi-touch display    -   800:1 contrast ratio (typical)    -   500 cd/m2 max brightness (typical)    -   Fingerprint-resistant oleophobic coating on front and back    -   Support for display of multiple languages and characters        simultaneously    -   5-megapixel iSight camera    -   Video recording, HD (720p) up to 30 frames per second with audio    -   VGA-quality photos and video at up to 30 frames per second with        the front camera    -   Tap to focus video or still images    -   LED flash    -   Photo and video geotagging    -   Built-in rechargeable lithium-ion battery    -   Charging via USB to computer system or power adapter    -   Talk time: Up to 20 hours on 3G, up to 14 hours on 2G (GSM)    -   Standby time: Up to 300 hours    -   Internet use: Up to 6 hours on 3G, up to 10 hours on Wi-Fi    -   Video playback: Up to 10 hours    -   Audio playback: Up to 40 hours    -   Frequency response: 20 Hz to 22,000 Hz    -   Audio formats supported: AAC (8 to 320 Kbps), protected AAC        (from iTunes Store), HE-AAC, MP3 (8 to 320 Kbps), MP3 VBR,        audible (formats 2, 3, 4, audible enhanced audio, AAX, and        AAX+), Apple lossless, AIFF, and WAV    -   User-configurable maximum volume limit    -   Video out support with Apple digital AV adapter or Apple VGA        adapter; 576p and 480p with Apple component AV cable; 576i and        480i with Apple composite AV cable (cables sold separately)    -   Video formats supported: H.264 video up to 1080p, 30 frames per        second, main profile Level 3.1 with AAC-LC audio up to 160 Kbps,        48 kHz, stereo audio in .m4v, .mp4, and .mov file formats;        MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per        second, simple profile with AAC-LC audio up to 160 Kbps per        channel, 48 kHz, stereo audio in .m4v, .mp4, and .mov file        formats; motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 1020        pixels, 30 frames per second, audio in ulaw, PCM stereo audio in        .avi file format    -   Three-axis gyro    -   Accelerometer    -   Proximity sensor    -   Ambient light sensor, etc.

Embodiments of the present disclosure may be used with other electronicdevices. Examples of suitable electronic devices include a portableelectronic device such as a media player, a cellular phone, a personaldata organizer, or the like. In such embodiments, a portable electronicdevice may include a combination of the functionalities of such devices.In addition, an electronic device may allow a user to connect to andcommunicate through the Internet or through other networks such as localor wide area networks. For example, a portable electronic device mayallow a user to access the internet and to communicate using e-mail,text messaging, instant messaging, or using other forms of electroniccommunication. By way of example, the electronic device may be similarto an iPod having a display screen or an iPhone available from AppleInc.

In certain embodiments, a device may be powered by one or morerechargeable and/or replaceable batteries. Such embodiments may behighly portable, allowing a user to carry the electronic device whiletraveling, working, exercising, and so forth. In this manner, anddepending on the functionalities provided by the electronic device, auser may listen to music, play games or video, record video or takepictures, place and receive telephone calls, communicate with others,control other devices (e.g., via remote control and/or Bluetoothfunctionality), and so forth while moving freely with the device. Inaddition, the device may be sized such that it fits relatively easilyinto a pocket or the hand of the user. While certain embodiments of thepresent disclosure are described with respect to portable electronicdevices, it should be noted that the presently disclosed techniques maybe applicable to a wide array of other, less portable, electronicdevices and systems that are configured to render graphical data such asa desktop computer.

As shown, FIG. 15H includes a system diagram with a smart phone thatincludes an LED according to an embodiment of the present disclosure.The smart phone 15H06 is configured to communicate with a server 15H02in electronic communication with any forms of handheld electronicdevices. Illustrative examples of such handheld electronic devices caninclude functional components such as a processor 15H08, memory 15H10,graphics accelerator 15H12, accelerometer 15H14, communicationsinterface 15H11 (possibly including an antenna 15H16), compass 15H18,GPS chip 15H20, display screen 15H22, and an input device 15H24. Eachdevice is not limited to the illustrated components. The components maybe hardware, software or a combination of both.

In some examples, instructions can be input to the handheld electronicdevice through an input device 15H24 that instructs the processor 15H08to execute functions in an electronic imaging application. One potentialinstruction can be to generate an abstract of a captured image of aportion of a human user. In that case the processor 15H08 instructs thecommunications interface ISHII to communicate with the server 15H02(e.g., possibly through or using a cloud 15H04) and transfer data (e.g.,image data). The data is transferred by the communications interfaceISHII and either processed by the processor 15H08 immediately afterimage capture or stored in memory 15H10 for later use, or both. Theprocessor 15H08 also receives information regarding the display screen'sattributes, and can calculate the orientation of the device, e.g., usinginformation from an accelerometer 15H14 and/or other external data suchas compass headings from a compass 15H18, or GPS location from a GPSchip 15H20, and the processor then uses the information to determine anorientation in which to display the image depending upon the example.

The captured image can be rendered by the processor 15H08, by a graphicsaccelerator 15H12, or by a combination of the two. In some embodiments,the processor can be the graphics accelerator 15H12. The image can firstbe stored in memory 15H10 or, if available, the memory can be directlyassociated with the graphics accelerator 15H12. The methods describedherein can be implemented by the processor 15H08, the graphicsaccelerator 15H12, or a combination of the two to create the image andrelated abstract. An image or abstract can be displayed on the displayscreen 15H22.

FIG. 15I depicts an interconnection of components in an electronicdevice 15I00. Examples of electronic devices include an enclosure orhousing, a display, user input structures, and input/output connectorsin addition to the aforementioned interconnection of components. Theenclosure may be formed from plastic, metal, composite materials, orother suitable materials, or any combination thereof. The enclosure mayprotect the interior components of the electronic device from physicaldamage, and may also shield the interior components from electromagneticinterference (EMI).

The display may be a liquid crystal display (LCD), a light emittingdiode (LED) based display, an organic light emitting diode (OLED) baseddisplay, or some other suitable display. In accordance with certainembodiments of the present disclosure, the display may display a userinterface and various other images such as logos, avatars, photos, albumart, and the like. Additionally, in certain embodiments, a display mayinclude a touch screen through which a user may interact with the userinterface. The display may also include various functions and/or systemindicators to provide feedback to a user such as power status, callstatus, memory status, or the like. These indicators may be incorporatedinto the user interface displayed on the display.

In certain embodiments, one or more of the user input structures can beconfigured to control the device such as by controlling a mode ofoperation, an output level, an output type, etc. For instance, the userinput structures may include a button to turn the device on or off.Further, the user input structures may allow a user to interact with theuser interface on the display. Embodiments of the portable electronicdevice may include any number of user input structures includingbuttons, switches, a control pad, a scroll wheel, or any other suitableinput structures. The user input structures may work with the userinterface displayed on the device to control functions of the deviceand/or any interfaces or devices connected to or used by the device. Forexample, the user input structures may allow a user to navigate adisplayed user interface or to return such a displayed user interface toa default or home screen.

Certain device may also include various input and output ports to allowconnection of additional devices. For example, a port may be a headphonejack that provides for the connection of headphones. Additionally, aport may have both input and output capabilities to provide for theconnection of a headset (e.g., a headphone and microphone combination).Embodiments of the present disclosure may include any number of inputand/or output ports such as headphone and headset jacks, universalserial bus (USB) ports, IEEE-1394 ports, and AC and/or DC powerconnectors. Further, a device may use the input and output ports toconnect to and send or receive data with any other device such as otherportable electronic devices, personal computers, printers, or the like.For example, in one embodiment, the device may connect to a personalcomputer via an IEEE-1394 connection to send and receive data files suchas media files.

The depiction of an electronic device 15I00 encompasses a smart phonesystem diagram according to an embodiment of the present disclosure. Thedepiction of an electronic device 15I00 illustrates computer hardware,software, and firmware that can be used to implement the disclosuresabove. The shown system includes a processor 15I26, which isrepresentative of any number of physically and/or logically distinctresources capable of executing software, firmware, and hardwareconfigured to perform identified computations. A processor 15I26communicates with a chipset 15I28 that can control input to and outputfrom processor 15I26. In this example, chipset 15I28 outputs informationto display screen 15I42 and can read and write information tonon-volatile storage 15I44, which can include magnetic media and solidstate media, and/or other non-transitory media, for example. Chipset15I28 can also read data from and write data to RAM 15I46. A bridge15I32 for interfacing with a variety of user interface components can beprovided for interfacing with chipset 15I28. Such user interfacecomponents can include a keyboard 15I34, a microphone 15I36,touch-detection-and-processing circuitry 15I38, a pointing device 15I40such as a mouse, and so on. In general, inputs to the system can comefrom any of a variety of machine-generated and/or human-generatedsources.

Chipset 15I28 also can interface with one or more data networkinterfaces 15I30 that can have different physical interfaces. Such datanetwork interfaces 15I30 can include interfaces for wired and wirelesslocal area networks, for broadband wireless networks, as well aspersonal area networks. Some applications of the methods for generating,displaying and using the GUI disclosed herein can include receiving dataover a physical interface 15I31 or be generated by the machine itself bya processor 15I26 analyzing data stored in non-volatile storage 15I44and/or in memory or RAM 15I46. Further, the machine can receive inputsfrom a user via devices such as a keyboard 15I34, microphone 15I36,touch-detection-and-processing circuitry 15I38, and pointing device15I40 and execute appropriate functions such as browsing functions byinterpreting these inputs using processor 15I26.

Assessing the impact of a light-emitting system on the circadian cyclemay be performed in a variety of ways, including using medical orclinical trials. In such trials, various physiological signals relatedto the circadian cycle may be monitored for subjects exposed to thelight-emitting system. For instance, it is possible to measure themelatonin suppression in the saliva or blood of the subjects. Otherphysiological signals, including various hormones, may be measured fromsaliva or blood samples or in other tests. Such protocols are known tothose skilled in the art and are discussed in scientific publications. Aspecific physiological response (such as the level of a specifichormone) may be targeted in such tests, especially for responses knownto correlate to a specific medical condition and/or a condition known orbelieved to be associated with the spectral content of light.

For instance, Brainard discloses a protocol for measuring the melatoninsuppression under light exposure. Some steps of the protocol are asfollows.

-   -   Subjects with normal vision are selected.    -   At midnight, the subjects enter a dimly lit room, their pupils        are dilated and they wait for a period of 2 hrs.    -   A blood sample if taken.    -   The subjects are exposed to the test light for 90 min, and a        second blood sample is taken.    -   The melatonin content in the blood samples is determined, and        the relative decrease in melatonin compared to that in a control        experiment (e.g., no light exposure).

Other testing protocols can be found in various publications such as,for example, in West et al.; in “Blue light from light-emitting diodeselicits a dose-dependent suppression of melatonin in humans” J. Appl.Physiol. 110, 619-626 (2011)).

While the present disclosure focuses on light-emitting diode devices, itcan be appreciated that the invention also applies to lighting ordisplay systems based on laser diode devices.

In certain embodiments provided by the present disclosure, light sourcescomprise at least one first LED emission source characterized by a firstemission; and at least one second LED emission source characterized by asecond emission; wherein the first emission and the second emission areconfigured to provide a first combined emission and a second combinedemission; the first combined emission is characterized by a first SPDand fractions Fv1 and Fc1; the second combined emission is characterizedby a second SPD and fractions Fv2 and Fc2; Fv1 represents the fractionof power of the first SPD in the wavelength range from 400 nm to 440 nm;Fc1 represents the fraction of power of the first SPD in the wavelengthrange from 440 nm to 500 nm; Fv2 represents the fraction of power of thesecond SPD in the wavelength range from 400 nm to 440 nm; Fc2 representsthe fraction of power of the second SPD in the wavelength range from 440nm to 500 nm; the first SPD and the second SPD have a color renderingindex above 80; Fv1 is at least 0.05; Fc2 is at least 0.1; and Fc1 isless than Fc2 by at least 0.02.

In certain embodiments of a light source, the first combined emission ischaracterized by a first circadian stimulation; the second combinedemission is characterized by a second circadian stimulation; and thesecond circadian stimulation is at least twice the first circadianstimulation.

In certain embodiments of a light source, the first LED emission sourcecomprises at least one LED characterized by a peak emission in the range405 nm to 430 nm.

In certain embodiments of a light source, the first emission and thesecond emission are configured to provide a third combined emission; thethird combined emission is characterized by a third SPD, a fraction Fv3,a fraction Fc3, and a third circadian stimulation; Fv3 represents thefraction of power of the third SPD in the wavelength range from 400 nmto 440 nm; Fc3 represents the fraction of power of the third SPD in thewavelength range from 440 nm to 500 nm; the third SPD has a coloringrendering index above 80; and the first circadian stimulation and thethird circadian stimulation are different.

In certain embodiments of a light source, the second emission comprisesblue emission from a wavelength down-conversion material.

In certain embodiments of a light source, the second emission comprisesdirect blue emission from an LED.

In certain embodiments of a light source, one of the combined emissionsinduces a circadian stimulation similar to a circadian stimulation of aD65 reference illuminant.

In certain embodiments of a light source, one of the combined emissionsinduces a circadian stimulation that is less than a circadianstimulation of a CIE A reference illuminant.

In certain embodiments of a light source, the at least one first LEDemission source and the at least one second LED emission source areconfigured in an intermixed physical arrangement.

In certain embodiments of a light source, each of the first SPD and thesecond SPD is characterized by a chromaticity within the white lightbounding region 514 of FIG. 5B.

In certain embodiments of a light source, each of the first SPD and thesecond SPD is characterized by a chromaticity bounded by ±0.005 of aPlanckian loci and by ±0.005 of a minimum-hue-shift curve in a CIEchromaticity diagram.

In certain embodiments of a light source, each of the first SPD and thesecond SPD is characterized by a chromaticity within +/−five Du′v′points of a Planckian loci.

In certain embodiments of a light source, exposure of a subject to thesecond SPD with an illuminance of 100 lx for ninety minutes results in asuppression of blood melatonin concentration in the subject of at least20%.

In certain embodiments of a light source, exposure of a subject to thefirst SPD with an illuminance of 100 lx for ninety minutes results in asuppression blood melatonin concentration in the subject of at most 20%.

In certain embodiments of a light source, Fc1 is at most 0.06

In certain embodiments, a display system comprises a first LED emissionsource characterized by a first emission; and a display configured toemit a first SPD characterized by a first fraction Fv1 of power in therange 400 nm to 435 nm; wherein, the display system is characterized bya color gamut of at least 70% of NTSC; the first SPD is substantiallywhite with a CCT in a range from 3000K to 9000K; and Fv1 is at least0.05.

In certain embodiments of a display system, the display comprises anemission spectrum characterized by a circadian stimulation that is lessthan a circadian stimulation of a reference illuminant having the sameCCT.

In certain embodiments of a display system, the display system furthercomprises a color filter set and a liquid crystal display.

In certain embodiments of a display system, the first SPD ischaracterized by a peak in the wavelength range from 400 nm to 435 nm ata wavelength w; the color filter set comprises a blue filtercharacterized by a maximum transmission Tm, and by a transmission Tw atwavelength w; and Tw/Tm>0.8.

In certain embodiments, a display system further comprises a second LEDemission source characterized by a second emission, wherein a ratio ofthe first emission and the second emission are configured to be adjustedto change a circadian stimulation.

In certain embodiments of a display system, the display system isconfigured for use with a TV, desktop PC, notebook PC, laptop PC,tablet, smartphone, MP3 player.

In certain embodiments of a display system, less than 5% of the power ofthe first SPD is in a wavelength range from 440 nm to 500 nm.

In certain embodiments, a light source comprises an LED deviceconfigured to emit a primary emission; one or more wavelength conversionmaterials optically coupled to the primary emission; wherein a portionof the primary emission is absorbed by the wavelength conversionmaterials to produce a secondary emission; wherein a combination of theprimary emission and the secondary emission produces white lightcharacterized by an SPD having a CCT and a color rendering index;wherein at least 5% of the SPD is in a wavelength range from 400 nm to435 nm; wherein a circadian stimulation of the SPD is less than 80% of acircadian stimulation of a reference illuminant having the same colortemperature; and wherein the white light is characterized by a colorrendering index above 80.

In certain embodiments, of a light source, the primary emission ischaracterized by a peak wavelength between 405 nm and 425 nm.

In certain embodiments, a lighting system comprises an LED deviceconfigured to emit a primary emission characterized by a primary SPD; atleast one phosphor optically coupled to the primary emission, whereinthe at least one phosphor is characterized by saturable absorptionwithin a blue-cyan wavelength region; wherein the LED device isconfigured to be controlled by a power signal configured to dim theprimary emission; wherein at a first power level the system emits afirst SPD characterized by a first fraction fc1 of spectral power in awavelength range from 440 nm to 500 nm and a first CCT; wherein at asecond power level the system emits a second SPD characterized by asecond fraction fc2 of spectral power in a wavelength range from 440 nmto 500 nm and a second CCT; and wherein the second power level is lessthan the first power level and the second fraction fc2 is less than 80%of the first fraction fc1.

In certain embodiments of a lighting system, the second CCT is at least500K less than the first CCT.

In certain embodiments of a lighting system, where at least 5% of theprimary SPD is in a wavelength range from 400 nm to 435 nm.

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the claims are not to be limited to the details given herein, butmay be modified within the scope and equivalents thereof.

What is claimed is:
 1. A light emitter comprising: one or more LEDsconfigured to emit LED light, said one or more LEDs comprising at leasta violet LED configured to emit violet light with a peak wavelengtharound 405 nm; at least one phosphor configured convert a fraction ofsaid LED light to emit converted light; and wherein said light emitteremits an emitted light comprising a combination of at least saidconverted light and a fraction of said LED light, said emitted lighthaving a spectral power distribution (SPD), said SPD having a firstpower from 350 nm to 850 nm, and a second power from 400 nm to about 440nm, wherein said second power is at least 15% of said first power, andwherein said SPD has a color rendering index (CRI) greater than 80, andan R9 greater than
 0. 2. The light emitter of claim 1, wherein saidsecond power is at least 20% of said first power.
 3. The light emitterof claim 1, wherein said second power is at least 25% of said firstpower.
 4. The light emitter of claim 1, wherein said R9 is at least 50.5. The light emitter of claim 1, wherein said emitted light has achromaticity within +/−five Du′v′ points of the Planckian locus.
 6. Thelight emitter of claim 5, wherein said emitted light has a chromaticitybelow the Planckian locus.
 7. The light emitter of claim 1, wherein saidSPD has a CCT ranging from about 3000K to about 9000K.
 8. The lightemitter of claim 1, wherein said SPD has a local peak corresponding tosaid violet light.
 9. The light emitter of claim 1, wherein said one ormore LEDs also comprises at least one second LED to emit second lightdifferent from said violet light.
 10. The light emitter of claim 9,wherein said second light is blue light.
 11. The light emitter of claim9, wherein said one or more LEDs are configured to operate in two ormore modes, in a first mode, said violet LED and said second LED aredriven at a first ratio relative to each other resulting in said emittedlight, and in a second mode, said violet LED and said second LED aredriven at a second ratio relative to each other resulting in secondemitted light, wherein said second emitted light has a second SPD, saidsecond SPD has a third power from 350 nm to 850 nm, a fourth power from400 nm to about 440 nm, and a fifth power from 440 nm to 500 nm, whereinsaid fourth power is less than 10% of said third power.
 12. The lightemitter of claim 11, wherein said fifth power is at least 10% of saidthird power.
 13. The light emitter of claim 1, wherein said at least onephosphor comprises two or more phosphors.
 14. The light emitter of claim1, wherein said at least one phosphor is pumped by said violet light.15. The light emitter of claim 1, wherein said one or more LEDs alsocomprises at least one second LED to emit second light different fromsaid violet light, wherein said at least one phosphor is pumped by saidsecond light.